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 A364620 #7 Jul 30 2023 09:20:00
%S A364620 1,3,12,67,449,3315,25963,211685,1777410,15263446,133427406,
%T A364620 1183336278,10620959908,96292118665,880540044576,8112042293581,
%U A364620 75218203558241,701439747294225,6574348389693202,61897799517155325,585138783209680944,5551797662571097495
%N A364620 G.f. satisfies A(x) = 1/(1-x)^2 + x*A(x)^3.
%F A364620 a(n) = Sum_{k=0..n} binomial(n+3*k+1,4*k+1) * binomial(3*k,k) / (2*k+1).
%o A364620 (PARI) a(n) = sum(k=0, n, binomial(n+3*k+1, 4*k+1)*binomial(3*k, k)/(2*k+1));
%Y A364620 Cf. A086616, A364621.
%K A364620 nonn
%O A364620 0,2
%A A364620 _Seiichi Manyama_, Jul 30 2023