This sounds like the 2011 4chan post that solved the Haruhi superpermutation problem
<a href="https://boingboing.net/2025/03/07/anonymous-anime-fan-solves-complex-superpermutation-puzzle-on-4chan.html" rel="nofollow">https://boingboing.net/2025/03/07/anonymous-anime-fan-solves...</a>