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 A189842 #6 Sep 12 2015 11:00:25 %S A189842 1,2,6,24,120,720,4800,34752,280512,2528256,25282560,278323200, %T A189842 3242649600,40330371072,536528954880,7633092132864 %N A189842 Number of ways to place n nonattacking composite pieces rook + rider[6,6] on an n X n chessboard. %C A189842 a(n) is also number of permutations p of 1,2,...,n satisfying |p(j+6k)-p(j)|<>6k for all j>=1, k>=1, j+6k<=n %H A189842 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 A189842 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fairy_chess_piece">Fairy chess piece</a> %Y A189842 Cf. A189271, A000170, A189838, A189839, A189840, A189841 %K A189842 nonn,hard %O A189842 1,2 %A A189842 _Vaclav Kotesovec_, Apr 29 2011