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 A189837 #15 Aug 01 2022 08:08:55 %S A189837 1,2,2,8,12,22,58,276,648,2304,6508,24528,96402,466922,2271738, %T A189837 13723826,76579326,512425626,3281233020,24654941268,175398054696 %N A189837 Number of ways to place n nonattacking composite pieces rook + rider[1,2] on an n X n chessboard. %C A189837 (In fairy chess the rider [1,2] is called a Nightrider, Rook + Nightrider = Waran.) %C A189837 a(n) is also the number of permutations p of 1,2,...,n satisfying |p(i+k) - p(i)| <> 2k AND |p(j+2k) - p(j)| <> k for all i >= 1, j >= 1, k >= 1, i+k <= n, j+2k <= n. %H A189837 V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Number of ways of placing non-attacking queens, kings, bishops and knights</a> (in English and Czech). %H A189837 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fairy_chess_piece">Fairy chess piece</a> %Y A189837 Cf. A102388, A000170. %K A189837 nonn,hard %O A189837 1,2 %A A189837 _Vaclav Kotesovec_, Apr 29 2011