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 A195591 #20 Aug 31 2025 10:49:18
%S A195591 16,90,344,1082,3036,7918,19648,47058,109796,251126,565512,1257754,
%T A195591 2769196,6046014,13107536,28246370,60555636,129237382,274727320,
%U A195591 581960106,1228931516,2587886030,5435818464,11391730162,23823647236,49727668758,103616086568
%N A195591 Number of ways to place 3n nonattacking kings on a vertical cylinder 6 X 2n.
%C A195591 Vertical cylinder: a chessboard where it is supposed that the columns 1 and 6 are in contact (number of columns = 6, number of rows = 2n).
%H A195591 Ray Chandler, <a href="/A195591/b195591.txt">Table of n, a(n) for n = 1..3305</a>
%H A195591 V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Non-attacking chess pieces</a>.
%H A195591 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (6,-13,12,-4).
%F A195591 Recurrence: a(n) = -4*a(n-4) + 12*a(n-3) - 13*a(n-2) + 6*a(n-1).
%F A195591 G.f.: x*(1+10*x+7*x^2)/((x-1)^2*(2*x-1)^2).
%F A195591 a(n) = (31*n - 65)*2^n + 18*n + 66.
%F A195591 E.g.f.: exp(x)*(48*(1 - exp(x)) + x*(18 + 31*exp(x))). - _Stefano Spezia_, Aug 31 2025
%t A195591 LinearRecurrence[{6,-13,12,-4},{16,90,344,1082},30] (* _Harvey P. Dale_, Nov 15 2021 *)
%Y A195591 Cf. A194645, A061594, A137432.
%K A195591 nonn,easy,changed
%O A195591 1,1
%A A195591 _Vaclav Kotesovec_, Sep 21 2011