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 A352010 #6 Mar 01 2022 07:28:12
%S A352010 1,1,1,-2,-5,1,16,94,127,-317,-1103,-2258,160,18922,39664,-163064,
%T A352010 -524489,-187577,1711591,12353800,18926119,-53449661,-207918068,
%U A352010 -15689834,960812728,3295064650,3870965368,-33248209286,-96830084768,17122290256,505711364524
%N A352010 a(0) = 1; a(n) = Sum_{k=0..floor((n-1)/2)} (-3)^k * a(k) * a(n-2*k-1).
%F A352010 G.f. A(x) satisfies: A(x) = 1 / (1 - x * A(-3*x^2)).
%t A352010 a[0] = 1; a[n_] := a[n] = Sum[(-3)^k a[k] a[n - 2 k - 1], {k, 0, Floor[(n - 1)/2]}]; Table[a[n], {n, 0, 30}]
%t A352010 nmax = 30; A[_] = 0; Do[A[x_] = 1/(1 - x A[-3 x^2]) + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
%Y A352010 Cf. A015098, A101912, A352009, A352011.
%K A352010 sign
%O A352010 0,4
%A A352010 _Ilya Gutkovskiy_, Feb 28 2022