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 A189879 #6 Sep 12 2015 11:00:25 %S A189879 1,0,0,2,2,4,28,0,20,20,180,520,1888,6016,22480,105236,433500,1933604, %T A189879 9687268,50998366,269523272,1507984008 %N A189879 Number of ways to place n nonattacking composite pieces queen + rider[3,4] on an n X n chessboard. %C A189879 a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+3k)-p(i)|<>4k AND |p(j+4k)-p(j)|<>3k AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+3k<=n, j+4k<=n, m+k<=n %H A189879 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 A189879 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fairy_chess_piece">Fairy chess piece</a> %Y A189879 Cf. A102388, A189874, A189877, A189858 %K A189879 nonn,hard %O A189879 1,4 %A A189879 _Vaclav Kotesovec_, Apr 29 2011