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 A289788 #17 Aug 11 2017 18:52:45
%S A289788 1,6,31,156,785,3954,19919,100344,505489,2546430,12827791,64620756,
%T A289788 325530881,1639881066,8260997855,41615265264,209639359969,
%U A289788 1056070674294,5320018479679,26799907726860,135006120168881,680101314855906,3426050596003631,17258932500172776
%N A289788 a(n) = (1/2)*A289787(n).
%H A289788 Clark Kimberling, <a href="/A289788/b289788.txt">Table of n, a(n) for n = 0..1000</a>
%H A289788 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (6, -6, 6, -1)
%F A289788 G.f.: (1 + x^2)/(1 - 6 x + 6 x^2 - 6 x^3 + x^4).
%F A289788 a(n) = 6*a(n-1) - 6*a(n-2) + 6*a(n-3) - a(n-4).
%t A289788 z = 60; s = 2*x/(1 - x)^2; p = 1 - s - s^2;
%t A289788 Drop[CoefficientList[Series[s, {x, 0, z}], x], 1] (* A005843 *)
%t A289788 u = Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1] (* A289787 *)
%t A289788 u/2 (* A289788 *)
%Y A289788 Cf. A289780, A289787.
%K A289788 nonn,easy
%O A289788 0,2
%A A289788 _Clark Kimberling_, Aug 10 2017