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 A189868 #6 Sep 12 2015 11:00:25 %S A189868 1,0,0,2,0,0,0,0,0,4,64,384,2936,10720,62664,420272,2540584,16373760, %T A189868 115200080,868564232,6708291360 %N A189868 Number of ways to place n nonattacking composite pieces queen + leaper[2,4] on an n X n chessboard. %C A189868 a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2)-p(i)|<>4 AND |p(j+4)-p(j)|<>2 AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+2<=n, j+4<=n, m+k<=n %H A189868 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 A189868 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fairy_chess_piece">Fairy chess piece</a> %Y A189868 Cf. A051223, A189865, A189867, A189566 %K A189868 nonn,hard %O A189868 1,4 %A A189868 _Vaclav Kotesovec_, Apr 29 2011