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 A378411 #20 Dec 08 2024 10:19:32
%S A378411 1,2,3,8,19,50,137,380,1088,3152,9270,27576,82794,250700,764454,
%T A378411 2345688,7237318,22438988,69876356,218456216,685400835,2157396738,
%U A378411 6810801959,21559694364,68417766207,217617573110,693655532081,2215401956720,7088605614314,22720370822508
%N A378411 G.f. A(x) satisfies A(x) = ( 1 + x * (1 + x*A(x)^(3/2)) )^2.
%F A378411 a(n) = 2 * Sum_{k=0..n} binomial(3*(n-k)+2,k) * binomial(k,n-k)/(3*(n-k)+2).
%F A378411 G.f.: A(x) = B(x)^2 where B(x) is the g.f. of A019497.
%o A378411 (PARI) a(n, r=2, s=1, t=0, u=3) = r*sum(k=0, n, binomial(t*k+u*(n-k)+r, k)*binomial(s*k, n-k)/(t*k+u*(n-k)+r));
%Y A378411 Cf. A371607, A371608.
%Y A378411 Cf. A019497.
%K A378411 nonn
%O A378411 0,2
%A A378411 _Seiichi Manyama_, Dec 08 2024