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 A189874 #6 Sep 12 2015 11:00:25 %S A189874 1,0,0,2,10,0,0,4,8,28,100,186,624,1720,7288,30666,100220,360208, %T A189874 1517804,7302336,29429672,139854636,753288744 %N A189874 Number of ways to place n nonattacking composite pieces queen + rider[1,4] on an n X n chessboard. %C A189874 (in fairy chess the rider [1,4] is called a Girafferider) %C A189874 a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+k)-p(i)|<>4k AND |p(j+4k)-p(j)|<>k AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+k<=n, j+4k<=n, m+k<=n %H A189874 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 A189874 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fairy_chess_piece">Fairy chess piece</a> %Y A189874 Cf. A102388, A189873, A189851 %K A189874 nonn,hard %O A189874 1,4 %A A189874 _Vaclav Kotesovec_, Apr 29 2011