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 A189563 #11 Mar 19 2017 15:59:54 %S A189563 1,1,2,6,24,48,182,868,5752,37156,296944,2738820,28894206,335399468, %T A189563 4285522402,59536763892,892785282788 %N A189563 Number of permutations p of 1,2,...,n satisfying |p(i+1)-p(i)|<>4 and |p(j+4)-p(j)|<>1 for all i=1..n-1, j=1..n-4. %C A189563 a(n) is also the number of ways to place n nonattacking pieces rook + leaper[1,4] on an n X n chessboard (in fairy chess the leaper[1,4] is called a giraffe). %H A189563 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) %F A189563 Asymptotic: a(n)/n! ~ 1/e^4. %Y A189563 Cf. A137774, A189358. %K A189563 nonn,more,hard %O A189563 0,3 %A A189563 _Vaclav Kotesovec_, Apr 23 2011