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Please, please, if you recognise this, *please* don't give it away for anyone else.

Does anyone recognise the "caterpillars" on this ?

Please reply via PM if you get it, but feel free to speculate if you choose.

That moment when opening an image in the gimp takes your machine load to over 17:


What's interesting about this complicated braid? The answer is that it is trivial, but not trivially trivial. It was found by Patrick Dehornoy, who has just died. I've written a thread about him, but am reposting this because it got buried at the end.


Repeatedly I am baffled by the Virgin Trains booking site. Here's another example where I'm unable to explain how they do this:

So we made a purchase, and it was going to be delivered. The company has been great about keeping us informed. Also, we got this in an email:

Seen today - hard to disagree:

To the Times:

During my many years in the classroom my colleagues and I rarely noticed if the headteacher was not in school. However, if the tea lady was absent everyone knew.

Dr N Flavell, Sheffield

That's it - MathsJam is about to start. 176 delegates, 52 talks, Cakes, Competition Competition, MathsJamJam, and more : ...

Watch for the tweets.

Here's a nice little challenge - what's the first false positive from this routine?

Found the photo! I've always *hated* selfies, and never look good in them, but here I am with @TheAntonDuBeke - as I say, a lovely man.

Suddenly realised that we are pretty much at the limit for the MathsJam weekend - let me know if you want to come but haven't paid.

Very simple code to generate left-truncatable primes - what would you do differently?

To assist @ChurchillHelp - who assure me that there won't be charges when I reply to their survey, here's a screenshot:

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