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 A189791 #13 Sep 12 2015 11:00:25
%S A189791 4,80,2688,132864,8647680,699678720,67711795200,7629571031040,
%T A189791 981168437329920,141817953779712000,22760391875493888000,
%U A189791 4016046336733347840000,772743693378451931136000,161027573368536472485888000,36127883615009765477842944000
%N A189791 Number of ways to place n nonattacking bishops on an 2n x 2n toroidal board.
%H A189791 Vincenzo Librandi, <a href="/A189791/b189791.txt">Table of n, a(n) for n = 1..200</a>
%H A189791 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 A189791 a(n)=2^n*n!*Sum[Binomial[n,i]^3,{i,0,n}].
%F A189791 Asymptotic: a(n) ~ 2^(4n+1)*(n-1)!/Pi/sqrt(3) ~ 2^(4n+1)*n^n/exp(n)*sqrt(2/(3*Pi*n)).
%F A189791 Recurrence: a(n) = ((14*n^2-14*n+4)*a(n-1) + 32*(n-1)^3*a(n-2))/n.
%t A189791 Table[2^n*n!*Sum[Binomial[n,i]^3,{i,0,n}],{n,1,20}]
%Y A189791 Cf. A189790, A002465, A000172.
%K A189791 nonn
%O A189791 1,1
%A A189791 _Vaclav Kotesovec_, Apr 27 2011