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 A178720 #7 Sep 12 2015 11:00:23
%S A178720 3,8,12,28,58,142,350,906,2320,6056,15778,41024,107132,280184,732998,
%T A178720 1918354,5019810,13141378,34398686,90045424,235729374,617126438,
%U A178720 1615633560,4229774958,11073514332,28990794770,75898640094,198704554772
%N A178720 Degree of denominator of GF for number of ways to place k nonattacking queens on an n X n toroidal board.
%H A178720 V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Non-attacking chess pieces</a>, 6ed, 2013
%F A178720 Explicit formula (Vaclav Kotesovec, Jun 05 2010), for k>2 : t(k) = 4*k+Sum[Sum[(2*j+1)*EulerPhi[i],{i,2*Fibonacci[k-j-1]+1,2*Fibonacci[k-j]}],{j,1,k-2}], Asymptotic formula: t(k) ~ 12/(5*Pi^2)*((1+Sqrt[5])/2)^(2*k+1) or t(k) ~ 6*(1+Sqrt[5])/Pi^2*Fibonacci[k]^2
%t A178720 Table[If[k > 1, 4*k + Sum[ Sum[(2*j + 1)*EulerPhi[i], {i, 2*Fibonacci[k - j - 1] + 1, 2*Fibonacci[k - j]}], {j, 1, k - 2}], 3], {k, 1, 20}]
%Y A178720 A172517, A172518, A172519, A173775, A000010, A000045, A178717.
%K A178720 nonn
%O A178720 1,1
%A A178720 _Vaclav Kotesovec_, Jun 07 2010