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 A364646 #8 Jul 31 2023 10:08:20
%S A364646 1,3,7,16,55,235,856,2664,9055,37417,151431,533452,1825972,7141860,
%T A364646 29778280,113688592,400940751,1499506693,6185139781,24862774872,
%U A364646 91529003839,334939413067,1338383383444,5510330536000,21217042841668,77850045234108,300471644949940
%N A364646 G.f. satisfies A(x) = 1/(1 - 4*x) - x*A(x)^3.
%F A364646 a(n) = Sum_{k=0..n} (-1)^k * 4^(n-k) * binomial(n+k,2*k) * binomial(3*k,k) / (2*k+1).
%o A364646 (PARI) a(n) = sum(k=0, n, (-1)^k*4^(n-k)*binomial(n+k, 2*k)*binomial(3*k, k)/(2*k+1));
%Y A364646 Cf. A364641, A364645, A364647.
%Y A364646 Cf. A001700, A349535.
%K A364646 nonn
%O A364646 0,2
%A A364646 _Seiichi Manyama_, Jul 31 2023