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 A189856 #6 Sep 12 2015 11:00:25 %S A189856 1,2,6,24,120,392,1810,10400,72228,589674,3823906,29420944,266232984, %T A189856 2711139976,30669073348,316482938974 %N A189856 Number of ways to place n nonattacking composite pieces rook + rider[2,5] on an n X n chessboard. %C A189856 a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2k)-p(i)|<>5k AND |p(j+5k)-p(j)|<>2k for all i>=1, j>=1, k>=1, i+2k<=n, j+5k<=n %H A189856 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 A189856 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fairy_chess_piece">Fairy chess piece</a> %Y A189856 Cf. A000170, A189854, A189855 %K A189856 nonn,hard %O A189856 1,2 %A A189856 _Vaclav Kotesovec_, Apr 29 2011