This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A365999 #11 Nov 04 2023 18:25:01 %S A365999 1,1,13,139,2546,51416 %N A365999 Number of free polyominoids with n cells, allowing right-angled corner-connections. %H A365999 Pontus von Brömssen, <a href="/A365999/a365999.svg">Illustration for sizes 1..3</a>. %H A365999 Wikipedia, <a href="https://en.wikipedia.org/wiki/Polyominoid">Polyominoid</a>. %H A365999 <a href="/index/Pol#polyominoes">Index entries for sequences related to polyominoes</a>. %Y A365999 See A365995 for further details and a table of related sequences. %Y A365999 Cf. A366000 (fixed). %Y A365999 23rd row of A366766. %K A365999 nonn,hard,more %O A365999 1,3 %A A365999 _Pontus von Brömssen_, Sep 26 2023