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 A366591 #11 Oct 14 2023 13:20:14
%S A366591 1,0,0,1,2,1,3,12,18,24,75,180,295,620,1612,3365,6580,15365,35728,
%T A366591 74906,163099,379242,848148,1848693,4187193,9583209,21417924,48067371,
%U A366591 109877922,250010451,564688551,1286128272,2944963788,6714338592,15313680087,35108572386
%N A366591 G.f. A(x) satisfies A(x) = 1 + x^3*(1+x)^2*A(x)^3.
%F A366591 a(n) = Sum_{k=0..floor(n/3)} binomial(2*k,n-3*k) * binomial(3*k,k)/(2*k+1).
%o A366591 (PARI) a(n) = sum(k=0, n\3, binomial(2*k, n-3*k)*binomial(3*k, k)/(2*k+1));
%Y A366591 Cf. A366221, A366590, A366592.
%Y A366591 Cf. A366555.
%K A366591 nonn
%O A366591 0,5
%A A366591 _Seiichi Manyama_, Oct 14 2023