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 A189851 #6 Sep 12 2015 11:00:25 %S A189851 1,2,6,24,48,182,868,5752,22952,131766,912964,7556978,52602390, %T A189851 432795244,4121203656,44335718598,416447624724 %N A189851 Number of ways to place n nonattacking composite pieces rook + rider[1,4] on an n X n chessboard. %C A189851 In fairy chess, the rider [1,4] is called a Girafferider. %C A189851 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 for all i>=1, j>=1, k>=1, i+k<=n, j+4k<=n %H A189851 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 A189851 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fairy_chess_piece">Fairy chess piece</a> %Y A189851 Cf. A000170, A189837, A189850 %K A189851 nonn,hard %O A189851 1,2 %A A189851 _Vaclav Kotesovec_, Apr 29 2011