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 A189869 #6 Sep 12 2015 11:00:25 %S A189869 1,0,0,2,10,4,28,20,56,72,288,1304,6368,22884,125864,755412,4565572, %T A189869 29862256,207238124,1540506028,11774180220 %N A189869 Number of ways to place n nonattacking composite pieces queen + leaper[2,5] on an n X n chessboard. %C A189869 a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2)-p(i)|<>5 AND |p(j+5)-p(j)|<>2 AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+2<=n, j+5<=n, m+k<=n %H A189869 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 A189869 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fairy_chess_piece">Fairy chess piece</a> %Y A189869 Cf. A051223, A189866, A189867, A189868, A189567 %K A189869 nonn,hard %O A189869 1,4 %A A189869 _Vaclav Kotesovec_, Apr 29 2011