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 A291386 #6 Oct 06 2017 13:09:28
%S A291386 2,11,54,252,1134,4977,21438,91017,381996,1588248,6552252,26853687,
%T A291386 109438938,443837799,1792373346,7211142612,28915704810,115603540605,
%U A291386 460942202070,1833459620517,7276826042712,28823185892016,113957884236024,449793742386627
%N A291386 a(n) = (1/3)*A099432(n+1).
%H A291386 Clark Kimberling, <a href="/A291386/b291386.txt">Table of n, a(n) for n = 0..1000</a>
%H A291386 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (6, -3, -18, -9)
%F A291386 G.f.: -(((1 + x) (-2 + 3 x + 3 x^2))/(-1 + 3 x + 3 x^2)^2).
%F A291386 a(n) = 6*a(n-1) - 3*a(n-2) - 18*a(n-3) - 9*a(n-4) for n >= 5.
%t A291386 z = 60; s = x + x^2; p = (1 - 3 s)^2;
%t A291386 Drop[CoefficientList[Series[s, {x, 0, z}], x], 1] (* A019590 *)
%t A291386 u = Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1] (* A099432 *)
%t A291386 u / 3 (* A291386 *)
%t A291386 LinearRecurrence[{6,-3,-18,-9},{2,11,54,252},30] (* _Harvey P. Dale_, Oct 06 2017 *)
%Y A291386 Cf. A019590, A291382, A099432.
%K A291386 nonn,easy
%O A291386 0,1
%A A291386 _Clark Kimberling_, Sep 04 2017