This is the Grünbaum–Rigby configuration (https://en.wikipedia.org/wiki/Gr%C3%BCnbaum%E2%80%93Rigby_configuration), three overlaid regular heptagrams with 21 points and lines, 4 points per line, and 4 lines per point. Klein studied it in the complex projective plane in 1879, but it wasn't known to have a nice real realization until Grünbaum and Rigby (1990). Wikipedia editor "Tomo" (I'll let you figure out who that is) started a new article a month ago, and now it's on the front page of Wikipedia in the "Did you know" section.
A Mastodon instance for maths people. The kind of people who make \(\pi z^2 \times a\) jokes.
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