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 A189864 #11 Aug 01 2022 08:08:59 %S A189864 1,0,0,0,0,0,0,0,0,4,56,176,1932,4188,26960,182456,1132064,7645784, %T A189864 58695136,470822912,3792417988,32440237692 %N A189864 Number of ways to place n nonattacking composite pieces queen + leaper[1,3] on an n X n chessboard. %C A189864 (In fairy chess, the leaper [1,3] is called a camel.) %C A189864 a(n) is also the number of permutations p of 1,2,...,n satisfying |p(i+1) - p(i)| <> 3 AND |p(j+3) - p(j)| <> 1 AND |p(m+k) - p(m)| <> k for all i >= 1, j >= 1, m >= 1, k >= 1, i+1 <= n, j+3 <= n, m+k <= n. %H A189864 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 A189864 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fairy_chess_piece">Fairy chess piece</a>. %Y A189864 Cf. A051223, A189358. %K A189864 nonn,hard %O A189864 1,10 %A A189864 _Vaclav Kotesovec_, Apr 29 2011