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 A189569 #9 Mar 19 2017 16:25:01 %S A189569 1,1,2,6,24,120,464,2274,13236,91760,740562,6541984,65632694, %T A189569 732880076,8995905626,120367234946 %N A189569 Number of permutations p of 1,2,...,n satisfying |p(i+3)-p(i)|<>5 and |p(j+5)-p(j)|<>3 for all i=1..n-3, j=1..n-5. %C A189569 a(n) is also the number of ways to place n nonattacking pieces rook + leaper[3,5] on an n X n chessboard. %H A189569 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 A189569 Asymptotic: a(n)/n! ~ 1/e^4. %Y A189569 Cf. A137774, A189358, A189563, A189564, A189565, A189566, A189567, A189568. %K A189569 nonn,more,hard %O A189569 0,3 %A A189569 _Vaclav Kotesovec_, Apr 23 2011