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 A189565 #9 Mar 19 2017 16:19:37 %S A189565 1,1,2,6,12,36,174,708,4334,31424,263732,2503296,26844578,316692056, %T A189565 4090634212,57274447458,863488976620 %N A189565 Number of permutations p of 1,2,...,n satisfying |p(i+2)-p(i)|<>3 and |p(j+3)-p(j)|<>2 for all i=1..n-2, j=1..n-3. %C A189565 a(n) is also the number of ways to place n nonattacking pieces rook + leaper[2,3] on an n X n chessboard (in fairy chess the leaper [2,3] is called a zebra). %H A189565 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 A189565 Asymptotic: a(n)/n! ~ 1/e^4. %Y A189565 Cf. A137774, A189358, A189563, A189564. %K A189565 nonn,more,hard %O A189565 0,3 %A A189565 _Vaclav Kotesovec_, Apr 23 2011