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 A130567 #25 Sep 06 2024 16:55:34
%S A130567 2,7,23,79,287,1087,4223,16639,66047,263167,1050623,4198399,16785407,
%T A130567 67125247,268468223,1073807359,4295098367,17180131327,68720001023,
%U A130567 274878955519,1099513724927,4398050705407,17592194433023,70368760954879
%N A130567 Expansion of x*(2 - 7*x + 2*x^2)/((1-x)*(1-4*x)*(1-2*x)).
%H A130567 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (7,-14,8).
%F A130567 a(n) = 2^(2*n - 1) + 2*a(n - 1) + 1.
%F A130567 From _R. J. Mathar_, Jun 13 2008: (Start)
%F A130567 O.g.f.: x*(2 - 7*x + 2*x^2)/((1-x)*(1-4*x)*(1-2*x)).
%F A130567 a(n) = A093069(n-2), n>1. (End)
%t A130567 f[n_Integer?Positive] := f[n] = 2^(2*n - 1) + 2*f[n - 1] + 1; f[0] = 2; Table[f[n], {n, 0, 30}]
%t A130567 CoefficientList[Series[x*(2-7x+2x^2)/((1-x)(1-4x)(1-2x)),{x,0,30}],x] (* _Harvey P. Dale_, Sep 07 2015 *)
%Y A130567 Cf. A093069, A099393, A028244.
%K A130567 nonn,easy
%O A130567 1,1
%A A130567 _Roger L. Bagula_, Aug 09 2007
%E A130567 New name from _Joerg Arndt_, Feb 08 2015