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 A379280 #12 Dec 20 2024 02:41:08
%S A379280 1,4,38,500,7601,125520,2187736,39608616,737651032,14040612502,
%T A379280 271931510448,5341639974490,106167131932708,2131125360950758,
%U A379280 43142742495766252,879810600033569754,18057207334571432048,372701480245014988624,7731178967720860156743
%N A379280 G.f. A(x) satisfies A(x) = ( (1 + x*A(x)^3) * (1 + x*A(x)) )^2.
%F A379280 G.f.: B(x)^2 where B(x) is the g.f. of A364333.
%F A379280 a(n) = Sum_{k=0..n} binomial(2*n+4*k+2,k) * binomial(2*n+4*k+2,n-k)/(n+2*k+1).
%o A379280 (PARI) a(n) = sum(k=0, n, binomial(2*n+4*k+2, k)*binomial(2*n+4*k+2, n-k)/(n+2*k+1));
%Y A379280 Cf. A379244, A379252, A379283.
%Y A379280 Cf. A364333, A379249.
%K A379280 nonn
%O A379280 0,2
%A A379280 _Seiichi Manyama_, Dec 19 2024