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 A291462 #6 Apr 07 2025 13:43:52
%S A291462 2,9,38,161,680,2872,12128,51214,216264,913228,3856328,16284284,
%T A291462 68764352,290374208,1226175744,5177825416,21864627616,92328709904,
%U A291462 389880441696,1646365025296,6952176889728,29357258422912,123968166486528,523485745182432,2210545926231680
%N A291462 a(n) = (1/2)*A291417(n).
%H A291462 Clark Kimberling, <a href="/A291462/b291462.txt">Table of n, a(n) for n = 0..1000</a>
%H A291462 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4, 2, -4, -2)
%F A291462 G.f.: -(((-1 + x) (1 + x) (2 + x))/(1 - 4 x - 2 x^2 + 4 x^3 + 2 x^4)).
%F A291462 a(n) = 4*a(n-1) + 2*a(n-2) - 4*a(n-3) - 2*a(n-4) for n >= 5.
%t A291462 z = 60; s = x + x^2; p = 1 - 4 s + 2 s^2;
%t A291462 Drop[CoefficientList[Series[s, {x, 0, z}], x], 1] (* A019590 *)
%t A291462 u = Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1] (* A291417 *)
%t A291462 u / 2 (*A291462)
%Y A291462 Cf. A019590, A291382, A291417.
%K A291462 nonn,easy
%O A291462 0,1
%A A291462 _Clark Kimberling_, Sep 07 2017