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 A337512 #5 Aug 30 2020 07:12:35
%S A337512 1,-1,0,1,1,-6,4,13,-13,-61,124,120,-516,-352,2848,-923,-11337,10165,
%T A337512 49352,-88655,-159903,512430,450812,-2873276,-11660,13752804,-9160464,
%U A337512 -62238760,91526344,239932224,-620180224,-768156379,3683079807,1168683353
%N A337512 G.f. A(x) satisfies: A(x) = 1 - Sum_{k=1..3} (x * A(x))^k.
%F A337512 G.f.: A(x) = (1/x) * Series_Reversion(x / (1 - x - x^2 - x^3)).
%t A337512 nmax = 33; A[_] = 0; Do[A[x_] = 1 - Sum[(x A[x])^k, {k, 1, 3}] + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
%t A337512 nmax = 34; CoefficientList[(1/x) InverseSeries[Series[x/(1 - x - x^2 - x^3), {x, 0, nmax}], x], x]
%t A337512 b[m_, r_, k_] := b[m, r, k] = If[m + r == 0, 1, Sum[b[m - j, r + j - 1, k], {j, 1, Min[1, m]}] - Sum[b[m + j - 1, r - j, k], {j, 1, Min[k, r]}]]; a[n_] := b[0, n, 3]; Table[a[n], {n, 0, 33}]
%Y A337512 Cf. A000073, A007440, A036765, A337513, A337514.
%K A337512 sign
%O A337512 0,6
%A A337512 _Ilya Gutkovskiy_, Aug 30 2020