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 A087452 #34 May 09 2024 04:38:53
%S A087452 2,1,25,37,337,781,4825,14197,72097,242461,1107625,4017157,17308657,
%T A087452 65514541,273218425,1059392917,4338014017,17050729021,69106897225,
%U A087452 273715645477,1102998412177,4387586157901,17623567104025,70274600998837,281757406247137
%N A087452 G.f.: (2-x)/((1+3x)(1-4x)); e.g.f.: exp(4x) + exp(-3x); a(n) = 4^n + (-3)^n.
%C A087452 Generalized Lucas-Jacobsthal numbers.
%H A087452 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (1,12).
%F A087452 a(n) = (-3)^n+4^n.
%F A087452 a(n) = a(n-1) + 12*a(n-2) for n > 1; a(0)=2, a(1)=1. - _Philippe Deléham_, Sep 19 2009
%F A087452 a(n) = 2*A053404(n) - A053404(n-1), n > 0. - _Ralf Stephan_, Jul 21 2013
%t A087452 CoefficientList[Series[(2 - z)/((1 + 3 z) (1 - 4 z)), {z, 0, 200}], z] (* _Vladimir Joseph Stephan Orlovsky_, Jun 11 2011 *)
%t A087452 LinearRecurrence[{1,12},{2,1},30] (* _Harvey P. Dale_, Nov 06 2022 *)
%o A087452 (PARI) polsym(x^2-x-12,50) \\ _Charles R Greathouse IV_, Jun 11 2011
%Y A087452 Cf. A014551, A053404, A087451.
%K A087452 easy,nonn
%O A087452 0,1
%A A087452 _Paul Barry_, Sep 06 2003