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 A152256 #16 May 22 2023 08:57:07
%S A152256 0,1,25,637,16810,450241,12123475,327035437,8827268020,238312027681,
%T A152256 6434206838125,173721623357437,4690466178937630,126642427965100321,
%U A152256 3419344125259375975,92322278513810982637,2492701404059145489640,67302936867273104276161
%N A152256 a(n) = (3^n - 1)*(3^n + 1)^2/32.
%H A152256 G. C. Greubel, <a href="/A152256/b152256.txt">Table of n, a(n) for n = 0..695</a>
%H A152256 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (40,-390,1080,-729).
%F A152256 a(n) = (3^n - 1)*(3^n + 1)^2/32.
%F A152256 From _G. C. Greubel_, May 22 2023: (Start)
%F A152256 a(n) = A002452(n)*A007051(n)/2.
%F A152256 a(n) = A003462(n)*A051500(n)/4.
%F A152256 G.f.: x*(1 -15*x +27*x^2)/((1-x)*(1-3*x)*(1-9*x)*(1-27*x)).
%F A152256 E.g.f.: (1/32)*(- exp(x) - exp(3*x) + exp(9*x) + exp(27*x)). (End)
%t A152256 Table[(9^n-1)*(3^n+1)/32, {n,0,30}]
%o A152256 (Magma) [(9^n-1)*(3^n+1)/32: n in [0..40]]; // _G. C. Greubel_, May 22 2023
%o A152256 (SageMath) [(9^n-1)*(3^n+1)/32 for n in range(41)] # _G. C. Greubel_, May 22 2023
%Y A152256 Cf. A002452, A003462, A007051, A051500.
%K A152256 nonn,easy
%O A152256 0,3
%A A152256 _Roger L. Bagula_, Dec 01 2008