Toots for svat@mathstodon.xyz account

Written by Shreevatsa R on 2025-01-11 at 04:11

I just heard that Siobhan Roberts is writing a biography of Donald Knuth, and I couldn't be more thrilled. (May even come out this year!)

Have seen bits of her biographies of Coxeter and Conway, and they were very good.

Had been sort of expecting/hoping this, ever since she wrote this great profile (wow already 6 years ago): https://www.nytimes.com/2018/12/17/science/donald-knuth-computers-algorithms-programming.html (https://archive.is/fPkcB)

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Written by Shreevatsa R on 2024-06-25 at 21:26

@mjd In case you didn't know (I didn't until it was pointed out to me), Pinterest pages have a "hidden in plain sight" link to where the image was copied from. In this case it goes to the blog post: https://theoccultandmagick.blogspot.com/2011/04/theban-alphabet.html (which has the image with link to: https://en.wikipedia.org/wiki/File:Theban.jpg)

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Written by Shreevatsa R on 2024-06-22 at 19:59

This fun lecture is like watching a magician at work: example after example of famous mathematical theorems that fall out from setting up an appropriate physical system and appealing to things like "no perpetual motion" or "entropy only increases". Great speaker. (Wish the audio recording quality was a bit better.)

https://www.youtube.com/watch?v=vNzmj6ryulI

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Written by Shreevatsa R on 2024-06-04 at 04:57

Wrote up a quick post mentioning Don Knuth's latest toy program he put up on his website: https://shreevatsa.net/post/dek-partition-square/ (Mostly just some context and explaining what the problem is; for anyone who'd like to just read the actual program directly, I have a typeset version at: https://shreevatsa.github.io/knuth-literate-programs/programs/perfect-partition-square.pdf )

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Written by Shreevatsa R on 2024-01-12 at 01:26

Earlier this week I started playing this CellTower game that many seem to be playing (my daughter says "ah you're playing word search"), and it's pretty fun.

I'm trying to optimize for time rather than for never making a wrong guess, per a suggestion I saw from @robinhouston. Today's puzzle took me 2 min 25 seconds (much of it trying to find the very first word!), so I think I must be getting better. Then again, on an older puzzle I tried earlier today I was stuck awfully long and it took 15 minutes, so maybe not just yet.

The result page shows a schematic diagram (below) of the correct and incorrect guesses one made while solving, but is otherwise unrelated to the gameplay.

[#]CellTower 617

⬛️⬛️⬛️⬇️⬛️⬇️⬛️⬛️⬛️⬛️⬛️⬛️⬛️⬛️

⬛️⬛️➡️⏹️➡️⏹️⬇️⬛️⬛️⬛️➡️➡️⬇️⬛️

➡️➡️⬆️⬛️⬛️⬛️➡️➡️➡️➡️⬆️⬛️➡️➡️ https://www.andrewt.net/puzzles/cell-tower/?p=617

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Written by Shreevatsa R on 2023-12-16 at 16:14

In 1964, someone named C. P. Willans (about whom nothing else is known AFAICT) published an absurd “formula for the nth prime number”, which is literally correct in a trolling kind of way.

[ p_n = 1 + \sum_{i=1}^{2^n} \left\lfloor \left(\frac{n}{\sum_{j=1}^i \left\lfloor\left(\cos \frac{(j-1)! + 1}{j} \pi\right)^2\right\rfloor }\right)^{1/n} \right\rfloor ]

I know this because I once posted an answer ("No") to the question “Is there a known mathematical equation to find the nth prime?”, at https://math.stackexchange.com/questions/1257 and get the occasional comment and downvote over the years, from people interested in this formula.

A couple of months ago I learned of an excellent video on YouTube that explains this formula step-by-step: https://www.youtube.com/watch?v=j5s0h42GfvM

I also wrote up a quick summary in text form, here: https://shreevatsa.net/post/willans-prime-formula/

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