I'm not sure I've seen this puzzle before, and I really like it:

We have n keys and n boxes. Each key fits only one box. We shuffle the keys and put one in each box. Then we randomly break open 1≤k≤n boxes. What is the probability that we can unlock all the other boxes?

I've been thinking about the fact that an n×n square grid has as many cells as a triangular lattice with n triangles on each side.
Is there a nice continuous bijection between them? When n is odd, you can at least keep one line of symmetry throughout.

continuing to mess around with bytebeat

Topologists at it again these mfers.

testing MathJax

testing MathJax

Is my daughter too young for NP-hard problems?

Ed Pegg, Jr has started updating mathpuzzle.com/ again! Hooray!

A Mastodon instance for maths people. The kind of people who make $$\pi z^2 \times a$$ jokes. Use $$ and $$ for inline LaTeX, and $ and $ for display mode.