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 A189860 #6 Sep 12 2015 11:00:25 %S A189860 1,2,6,24,120,720,3312,18688,127104,990208,8878016,89267712,789509184, %T A189860 7803741824,85447337472,1008717911040 %N A189860 Number of ways to place n nonattacking composite pieces rook + rider[3,6] on an n X n chessboard. %C A189860 a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+3k)-p(i)|<>6k AND |p(j+6k)-p(j)|<>3k for all i>=1, j>=1, k>=1, i+3k<=n, j+6k<=n %H A189860 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 A189860 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fairy_chess_piece">Fairy chess piece</a> %Y A189860 Cf. A000170, A189853, A189857 %K A189860 nonn,hard %O A189860 1,2 %A A189860 _Vaclav Kotesovec_, Apr 29 2011