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 A189855 #6 Sep 12 2015 11:00:25 %S A189855 1,2,6,24,60,208,1184,7840,36036,209664,1395480,10996728,83573220, %T A189855 723835856,7132494776,77976981216,790552134804 %N A189855 Number of ways to place n nonattacking composite pieces rook + rider[2,4] on an n X n chessboard. %C A189855 a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2k)-p(i)|<>4k AND |p(j+4k)-p(j)|<>2k for all i>=1, j>=1, k>=1, i+2k<=n, j+4k<=n %H A189855 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 A189855 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fairy_chess_piece">Fairy chess piece</a> %Y A189855 Cf. A000170, A189851, A189854, A189837 %K A189855 nonn,hard %O A189855 1,2 %A A189855 _Vaclav Kotesovec_, Apr 29 2011