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 A290907 #9 Aug 18 2017 15:52:02
%S A290907 0,1,4,13,44,152,524,1803,6204,21351,73480,252880,870280,2995049,
%T A290907 10307396,35472677,122078436,420130248,1445868996,4975926307,
%U A290907 17124540796,58933729999,202819133840,697997582240,2402143306640,8266923285201,28450434416004,97911543452733
%N A290907 a(n) = (1/3)*A290906(n).
%H A290907 Clark Kimberling, <a href="/A290907/b290907.txt">Table of n, a(n) for n = 0..1000</a>
%H A290907 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4, -3, 4, -1)
%F A290907 G.f.: x/(1 - 4 x + 3 x^2 - 4 x^3 + x^4).
%F A290907 a(n) = 4*a(n-1) - 3*a(n-2) + 4*a(n-3) - a(n-4).
%F A290907 a(n) = (1/3)*A290906(n) for n >= 0.
%t A290907 z = 60; s = x/(1 - x)^2; p = 1 - 3 s^2;
%t A290907 Drop[CoefficientList[Series[s, {x, 0, z}], x], 1] (* A000027 *)
%t A290907 u = Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1] (* A290906 *)
%t A290907 u/3 (* A290907 *)
%Y A290907 Cf. A000027, A290890, A290906.
%K A290907 nonn,easy
%O A290907 0,3
%A A290907 _Clark Kimberling_, Aug 17 2017