This Sudoku is (as always) easy with backtracking, but it seems harder than most of the ones that are hard enough for my program to need backtracking:

2 * * * * 9 * 1 *
* * * * * 3 * * *
* 3 5 * * * 2 * *

* * 4 * * * * * *
* 8 * 6 * * 3 9 *
* * * 8 2 * 7 * 4

* * 8 7 * * 4 * *
* 9 * * * 6 * 3 *
* * 1 * * * * * *

A Mastodon instance for maths people. The kind of people who make $\pi z^2 \times a$ jokes.

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