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 A352008 #5 Mar 01 2022 07:28:28
%S A352008 1,1,1,5,9,29,65,437,953,3981,10097,49829,123241,516349,1400737,
%T A352008 10203285,24698905,111642477,304787665,1704790917,4392726473,
%U A352008 19951366877,56296655617,336083829621,878995865721,3974885167949,11362790432305,60789762148453,165051865924137
%N A352008 a(0) = 1; a(n) = Sum_{k=0..floor((n-1)/2)} 4^k * a(k) * a(n-2*k-1).
%F A352008 G.f. A(x) satisfies: A(x) = 1 / (1 - x * A(4*x^2)).
%t A352008 a[0] = 1; a[n_] := a[n] = Sum[4^k a[k] a[n - 2 k - 1], {k, 0, Floor[(n - 1)/2]}]; Table[a[n], {n, 0, 28}]
%t A352008 nmax = 28; A[_] = 0; Do[A[x_] = 1/(1 - x A[4 x^2]) + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
%Y A352008 Cf. A000621, A015085, A352006, A352007.
%K A352008 nonn
%O A352008 0,4
%A A352008 _Ilya Gutkovskiy_, Feb 28 2022