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 A364647 #8 Jul 31 2023 10:08:24
%S A364647 1,4,13,38,135,677,3538,15868,63313,268430,1348190,7038185,33328258,
%T A364647 144159428,642323050,3213846836,16700677289,80935833050,363843867265,
%U A364647 1660048399600,8276473557820,42830085070355,210286731046320,967456811687945,4476690297795850
%N A364647 G.f. satisfies A(x) = 1/(1 - 5*x) - x*A(x)^3.
%F A364647 a(n) = Sum_{k=0..n} (-1)^k * 5^(n-k) * binomial(n+k,2*k) * binomial(3*k,k) / (2*k+1).
%o A364647 (PARI) a(n) = sum(k=0, n, (-1)^k*5^(n-k)*binomial(n+k, 2*k)*binomial(3*k, k)/(2*k+1));
%Y A364647 Cf. A364641, A364645, A364646.
%Y A364647 Cf. A026378.
%K A364647 nonn
%O A364647 0,2
%A A364647 _Seiichi Manyama_, Jul 31 2023