Christian Lawson-Perfect

Mathematician, koala fan, mathstodon.xyz admin,
⅓ of https://aperiodical.com. He/him

Public Key

npub12pjp03a8kt7sdvn4mge9ruf3rcqqdsy9hu7n8zdn3q9dgkhn875s0n9vae

NIP-05 Address

[email protected]

Profile Code

nprofile1qqs9qeqhc7nm9lgxkf6a5vj37yc3uqqxczzm70fn3xecszk5ttenl2gpz4mhxue69uhhyetvv9ujuerfw36x7tnsw43q9m5acc

Publishing to

relay.ditto.pub

Author Public Key

npub12pjp03a8kt7sdvn4mge9ruf3rcqqdsy9hu7n8zdn3q9dgkhn875s0n9vae

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Last Notes

2026-04-23 10:10:40 GMT

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@nprofile…2q04 did you see that she's been suspended for calling Keir Starmer a liar? https://www.bbc.co.uk/news/articles/cdrm752l03xo
cc @nprofile…y0gw

2026-03-05 14:42:40 GMT

I'm preparing a talk on accessibility of e-assessment, so I'm dredging my brain for memories of inaccessible questions I've seen.
If you have any suggestions, please tell me about them!

2026-02-17 11:57:00 GMT

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Nope, it's gone. I have a version from last May, but everything since is lost.

2026-02-17 11:06:22 GMT

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Why didn't I back it up? It takes a moment to set up. 😭

2026-02-17 11:04:28 GMT

Ahhhhhhhhh
I've accidentally deleted the kids' Minecraft world. I have no backups. I feel sick.
I deleted the directory containing it last Friday. I'm going to try a recovery usb and extundelete, but that's the only hope I'm clinging on to.

2026-02-12 10:30:56 GMT

Why is Rington's hot chocolate so yucky?

2026-02-11 08:10:58 GMT

Rate limited! by the arXiv

2026-02-10 16:45:55 GMT

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@nprofile…r0xq I bet there's a line "update MathJax" on their issue tracker, under a tonne of more urgent "deal with the nonsense the CS people are doing" issues

2026-02-10 15:46:21 GMT

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@nprofile…r0xq ... yes! (well, 2.7.3, to be precise)

2026-02-10 09:31:39 GMT

Welp, I had a meeting at 09:30 so of course after spending ten minutes replying to emails I couldn't get my brain to do anything else for 20 minutes.
Until I realised the meeting is 09:30 on Tuesday the 10th of *March*.
Stupid 28-day month.

2026-02-09 09:52:12 GMT

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@nprofile…y789 even ignoring the technical reasons not to cross the Irish sea twice, there are topological reasons not to make a loop line, aren't there? Like, we could currently have a loop Glasgow → Edinburgh → London → Liverpool → Manchester → Glasgow, but we don't, we have two separate lines.

2026-02-07 10:51:36 GMT

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@nprofile…vmfp (very big number) / (smaller number) returns 0 instead of (slightly less big number), which plain JS would return.
I don't know where Elm is doing this, but I have a vague memory of a warning somewhere in the docs.

2026-02-07 09:57:06 GMT

What a day to find out that #elmlang Ints are 32-bit!

2026-02-06 14:03:24 GMT

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Speedrunners might like to look at https://oeis.org/A173419

2026-02-06 10:34:28 GMT

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I think animating this as a big tower would be fun

2026-02-06 10:26:57 GMT

I have spent too much time this morning making a game about building numbers: https://number-builder.think.somethingorotherwhatever.com/

2026-02-05 16:16:34 GMT

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@nprofile…llgf hah, nothing so complicated!

2026-02-05 14:07:27 GMT

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@nprofile…7yy4 @nprofile…feml I've just given it a go, and it doesn't seem to be getting anywhere near a good packing. Oh well!

2026-02-04 15:17:16 GMT

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@nprofile…8npm eeeeeeeppp

2026-02-04 12:46:39 GMT

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@nprofile…feml super, thanks!

2026-02-04 12:30:33 GMT

I have a few complicated shapes that I want to #LaserCut. Is there an open source tool that will pack them in as small an area as possible?

2026-02-04 09:53:09 GMT

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@nprofile…7jv6 @nprofile…jp4z interesting! I've thought about this a lot in my work on accessibility, and never made the link to Browuer's fixed point theorem. (I was never any good at analysis)
There's a new function in CSS which is about as discontinuous as it can be: contrast-color() returns either 'white' or 'black': https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Values/color_value/contrast-color

2026-02-04 08:03:56 GMT

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The start of this thought was: can I count the number of Es on mastodon (its oulipo sad count)

2026-02-04 07:54:56 GMT

You have 406 unresolved childhood traumas.
⌷ Start crying now
⌷ Remind me at bedtime

2026-02-04 07:52:33 GMT

I had a useless thought in the shower:
I wonder what the entire corpus of toots looks like, in alphabetical order?
Wary of accidental PII disclosure, I've begun by writing all of my own statuses in alphabetical order: https://checkmyworking.com/posts/2026/02/every-toot-ive-ever-written-in-alphabetical-order/

2026-02-03 09:39:59 GMT

Microsoft Teams go 24 hours without asking me to sign in again challenge (impossible)

2026-01-31 18:03:10 GMT

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@nprofile…udvu too low in the sky for us 😔

2026-01-31 06:56:36 GMT

Are you a bad enough dude to overfill this \hbox?

2026-01-30 10:54:11 GMT

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@nprofile…w4kc only myself 😔

2026-01-29 13:42:44 GMT

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@nprofile…yhyk is this the mathstodon.xyz web interface? Which browser and OS are you using?

2026-01-29 10:07:24 GMT

Gang, it's only Thursday morning and I've already worked through the week's Emails That Require Attention, so I can get back to the fun thing I was working on last week! Hooray!

2026-01-27 14:32:42 GMT

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I was passed on to "the second level of support" and they've just changed the address, no ID necessary.
If I was a particularly awkward individual, I would take this as motivation to ask the information commissioner to look at their GDPR compliance. Where would my passport photo have gone, if I'd sent it?

2026-01-27 14:01:14 GMT

Currently locked in a battle of wills with OVH, trying to change the registered address for a domain name.
Their form doesn't work - it produces an error message in the console instead of submitting - so I created a support ticket. Now they say they want "the domain holder's ID" to change the address. I wouldn't have needed to give if the form worked.
Of course, being a UK subject, there is no one "ID". There are a variety of documents I could produce, very few of which I'm happy uploading a photo of to a random support ticket service.

2026-01-24 19:52:04 GMT

9814072356 is an interesting number: it's the largest square number (99066²) with no repeated digits.
From https://oeis.org/A392242, just added to the #OEIS.

2026-01-24 11:04:40 GMT

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@nprofile…my3l what's DCS?

2026-01-24 10:53:31 GMT

umm, red dead redemption 2 is 119GB?!?!

2026-01-23 12:58:24 GMT

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@nprofile…chm0 if only they had access to some good literature on effective search algorithms and metadata handling...

2026-01-21 16:02:31 GMT

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@nprofile…yctt they're mostly to the north of me. I'd go north-west at best.

2026-01-21 13:49:11 GMT

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@nprofile…4257 that has to be the winner!

2026-01-21 13:44:54 GMT

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if anyone can beat the three compass directions in the South East Northumberland Rail User Group, I'd be very happy to see it: https://www.senrug.co.uk/

2026-01-21 13:35:19 GMT

One thing we love to do in England is to compose compass directions to get really specific about the region we're interested in.
Durham Mathematics School says that it will take students from North North Yorkshire: https://durham-mathematics-school.org.uk/about-us/.
They don't narrow down Northumberland, but I can't see many students travelling down from Berwick: at 116km from Durham, it's further away than Selby in South North Yorkshire.

2026-01-21 11:33:30 GMT

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@nprofile…v0c7 if he's met powers before, then the base-10 münchausen numbers are fairly easy to explain, and not much harder to show they're finite: https://oeis.org/A046253

2026-01-21 08:54:57 GMT

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anybody who mentions cryptocurrency gets an immediate block, btw

2026-01-21 08:53:01 GMT

What happened to micropayments? Did everyone just decide it was too much friction, so went with ads instead?

2026-01-20 05:23:14 GMT

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@nprofile…9sln I'm not aware of any other issues, sorry.

2026-01-19 19:07:44 GMT

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@nprofile…vcny how much time are you spending on these? I decided to give it a go today before picking the kids up and in ten minutes got as far as "I can divide a square into 16×16 and use two hex digits as coordinates"

2026-01-19 08:53:01 GMT

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@nprofile…ck2y https://oeis.org/A114260 lists 13 pandigital numbers with this property

2026-01-19 08:15:56 GMT

5702631489 is an interesting number: 5702631489⁴ = 10575 50783 69274 13892 95697 10824 23634 08641.
It's the smallest number 𝑛 such that the decimal digits of 𝑛⁴ make up four copies of the digits of 𝑛.
And did you notice that 5702631489 uses every decimal digit?
Spotted in the new #OEIS sequence https://oeis.org/A391002, which lists numbers like this for each power.

2026-01-17 08:31:46 GMT

I'm having a lovely time doing play-doh tessellations.
#MathArt
https://media.mathstodon.xyz/media_attachments/files/115/909/499/148/634/516/original/a104009864c4785a.jpg
https://media.mathstodon.xyz/media_attachments/files/115/909/499/391/573/621/original/9438e024b2320a9e.jpg
https://media.mathstodon.xyz/media_attachments/files/115/909/499/579/514/006/original/33ec0267adfd0e32.jpg

2026-01-16 11:52:13 GMT

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I've realised that I can use the fact that I'm working with an equivalence relation, not just any matrix, to make this massively easier.
Now I'd better tell you the motivation for this: I'm thinking about how to assign a mark to a set of objects, when the student can choose how many objects to give.
I've made an interactive thing to explore this problem.
https://marking-sets.think.somethingorotherwhatever.com/
I'd really appreciate anyone's thoughts on this. I don't think there's a single best algorithm for this: I can think of situations where you'd want to reward or penalise things like extra or repeated answers differently.

2026-01-16 10:20:15 GMT

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@nprofile…w4kc ah yes, 'most'

2026-01-16 10:08:01 GMT

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no, I don't want the Hungarian algorithm

2026-01-16 10:04:20 GMT

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Welp, I think I have to repaint this door now
https://media.mathstodon.xyz/media_attachments/files/115/904/207/000/458/523/original/a3683068b9f2ed5f.jpg

2026-01-16 09:48:02 GMT

I'VE JUST USED A PERMANENT MARKER ON MY DOOR WHICH I USE AS A WHITEBOARD!!!!
😭

2026-01-16 09:40:38 GMT

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ahh, is the Hungarian algorithm the one I need?

2026-01-16 09:35:57 GMT

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I'm struggling to look back through the code I wrote 10 years ago.
I have an equivalence matrix of two sets of potentially different sizes: \(m_{ij}\) is 1 if \(A_i = B_j\), 0 otherwise.
I'd like to pick at one entry from each column so as to maximise the sum.
What's the name for this problem? Is it called something like "assignment" or "allocation"?

2026-01-16 09:30:28 GMT

oh no, I'm doing linear programming! Time to backtrack

2026-01-15 18:48:52 GMT

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@nprofile…920r thanks!
Earlier today @nprofile…klhg and I were discussing which languages have number words in alphabetical order, and which don't. We think French has a few.

2026-01-15 17:43:25 GMT

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@nprofile…hgxw which client is that?

2026-01-15 17:36:32 GMT

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@nprofile…hgxw you've got to fix whatever's going on with your client that removes the @ mentions. I only saw this because it has replies

2026-01-15 15:19:34 GMT

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@nprofile…chqj what about it, indeed! I can't imagine how it could take place as normal.

2026-01-15 12:32:17 GMT

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@nprofile…8npm this may be of use to you: https://random-emoji.think.somethingorotherwhatever.com/

2026-01-15 10:33:38 GMT

Idiotsyncratic: I do this in my own particular way, but my own particular way is wrong.

2026-01-15 09:32:49 GMT

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@nprofile…q33h that's a lovely idea! Lots of kids walk past our house on the way to school, so maybe I should set up a duck library too.

2026-01-14 13:57:12 GMT

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@nprofile…eljp yes, there are lots of mutually exclusive access adjustments.

2026-01-13 18:39:18 GMT

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@nprofile…fh5j denying permission for what?

2026-01-13 16:35:38 GMT

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@nprofile…fh5j that's the other version I tried

2026-01-13 14:03:10 GMT

Since I upgraded the graphics card in my Ubuntu PC to an AMD radeon 9060, Firefox doesn't do hardware acceleration any more.
From what I've found in forums and bug trackers, it looks like the snap version of Firefox is just waiting for newer versions of some libraries before it can do HW acceleration for AMD. I tried using the .deb version of Firefox instead, but that's no better and is even missing some software media decoders.
Does anyone else have a similar AMD card and working hardware acceleration? Is there anything I can do other than wait?

2026-01-11 08:51:42 GMT

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@nprofile…0n4h it picks at random from the entries at https://read.somethingorotherwhatever.com/

2026-01-11 08:14:58 GMT

My bot @nprofile…g03k largely only posts entries with open access contents, because the commercial publishers tend to block my request to check that the link still exists.
That means that some really interesting closed-access stuff is never posted. For example, today it would have picked "Theory and applications of the double-base number system" (https://ieeexplore.ieee.org/document/805158) but ieeexplore blocked it.
Should I change it to toot entries even when the request is blocked, at the expense of people without institutional access being unable to read the content, or should I leave things as they are?
(I do try to find legitimate open copies of papers where possible)

2026-01-11 06:42:09 GMT

49061132957714428902152118459264865645885092682687973 is an interesting number: it's the smallest integer not divisible by 2,3,5 or 7 and whose sum of proper divisors exceeds itself.
That's much bigger than I would have guessed!
A392235, "11-rough abundant numbers", just added to the #OEIS - https://oeis.org/A392235

2026-01-09 17:17:13 GMT

Pals, in five days I will turn 40. It's not one I've been especially looking forward to, but getting there is better than the other option.
If I can ask for a birthday present, please could you send me your best things to do with the number 40? (On my birthday, the 14th, not today).

2026-01-09 13:04:13 GMT

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@nprofile…7ejf the UK layout has that! Whenever I use a mac keyboard, which has " near the Enter key, I find it a real pain.

2026-01-09 10:10:40 GMT

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@nprofile…vhdw I spent a happy few days really diving deep into this a while ago: https://github.com/numbas/unicode-math-normalization

2026-01-09 09:49:54 GMT

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I suppose the remaining question is why ¬ is on standard UK keyboards.

2026-01-09 08:07:47 GMT

When's the last time you typed the character ¬ ?
Why do we use ! instead of ¬ for "not" in most programming languages?

2026-01-08 16:08:07 GMT

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@nprofile…mpn6 it won't! I'm building Docker images

2026-01-08 15:54:15 GMT

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and I'll end the day with downloading all of TeXLive again.

2026-01-08 14:31:25 GMT

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@nprofile…wyw7 eesh! It's all melted down here on Tyneside.

2026-01-08 13:50:09 GMT

I spent most of yesterday hacking away at my plasTeX fork, rebasing feature branches so they could be merged properly.
A glutton for punishment, I've spent today doing the same with the pylti1p3next module. After briefly knacking the `main` branch, I think I've got everything in order.
It feels like I've wasted two days, but really it was just hard work that wasn't fun.

2026-01-06 15:25:26 GMT

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@nprofile…6hny tu connais déjà les cercles dans le Sahara? https://www.google.co.uk/maps/@27.267429,-0.0941339,15847m/data=!3m1!1e3?entry=ttu&g_ep=EgoyMDI1MTIwOS4wIKXMDSoASAFQAw%3D%3D
C'est la forme la plus efficace pour l'irrigation puisqu'il n'y a pas de rivières.

2026-01-06 15:03:05 GMT

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@nprofile…2q04 The following works for me, in Firefox: await fetch('https://somethingorotherwhatever.com/index.html',{headers:{'Range': 'bytes=0-10' }}).
I get a response with content-length: 11.
If your request is similar to that, I'd look at the server to check it's interpreting the Range header correctly.

2026-01-06 13:08:04 GMT

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@nprofile…nmv5 yes, getting the temperature right is so hard!
I'd love one of those charts like the ones for baking cookies, with pictures of what it looks like if you have it too hot, or too cool, or not level, or get the z-offset wrong, etc.

2026-01-06 10:03:42 GMT

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@nprofile…58gl I think you could name anything academics do and find open source works better, but maybe I'm in a happy bubble!
It's definitely true in assessment. Commercial systems are expensive, limited and hard to work around when they go wrong. There are lots of widely-used, good, open-source assessment systems. The Moodle Quiz and associated plugins is I think the most popular example.
In my field, maths, there's STACK (https://stack-assessment.org/) and the thing I work on, @nprofile…mx3l.
Because they don't have to track users or depend on a central service, they can be hugely more robust and resilient.

2026-01-06 09:21:00 GMT

Over the past few days I've seen a few people saying they've been rate-limited while browsing GitHub.
I've just got back to work after the holiday, opened two links from GitHub emails, and I'm rate-limited. What heuristic are they using?!

2026-01-04 15:16:50 GMT

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@nprofile…s4qa have you played Rikudo? https://play.google.com/store/apps/details?id=com.rikudo.numbers

2025-12-31 10:32:28 GMT

Peepo!
https://media.mathstodon.xyz/media_attachments/files/115/813/718/807/916/094/original/aa69ac285a3aebaf.mp4

2025-12-29 12:09:08 GMT

is https://mail.google.com returning an empty document for anyone else, or just me?

2025-12-27 17:08:48 GMT

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@nprofile…63jn trop fort!

2025-12-27 16:12:02 GMT

Palindrometastic!
https://media.mathstodon.xyz/media_attachments/files/115/792/406/312/995/576/original/ee78a49020c76833.jpg

2025-12-25 14:55:20 GMT

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@nprofile…9l33 I can't work out how you did that. Did you have something with lots of nozzles so it all squeezed out at once, or is the icing viscous enough that it took a long time to settle?

2025-12-25 13:04:04 GMT

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@nprofile…qlqt @nprofile…pwph Merry Christmas! Thanks for being here!

2025-12-25 08:27:13 GMT

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@nprofile…vfj9 @nprofile…4x2g weird time to break out \varpi!

2025-12-24 17:55:35 GMT

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@nprofile…re6e there has to be a model of computation that uses jugs of water. Maybe rules about when you pour from one jug into another?

2025-12-24 17:34:53 GMT

It's 17:34, which means that today has progressed at the rate of two minutes per hour.

2025-12-24 11:08:35 GMT

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@nprofile…pa5k @nprofile…qggm bravo

2025-12-24 10:59:07 GMT

Bot idea: it toots a rorschach test image and AI generated alt text. Call it SchachGPT.

2025-12-24 10:57:47 GMT

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@nprofile…4wc6 we're doing Christmas jumper selfies, are we?
https://media.mathstodon.xyz/media_attachments/files/115/774/182/995/065/076/original/fcfa69347b0e682d.jpg

2025-12-23 16:45:31 GMT

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@nprofile…haa2 ooh, that reminds me I need to get the extra backup drive out of my mum's loft!

2025-12-23 16:33:41 GMT

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@nprofile…p9jf @nprofile…pwph that's a weird Monopoly board