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 A381906 #9 Mar 10 2025 06:58:10
%S A381906 1,3,15,100,787,6848,63583,617350,6191888,63650430,667043379,
%T A381906 7099806346,76538663840,833975952491,9169925032189,101616966476850,
%U A381906 1133736002540882,12724529836447420,143567856744995568,1627454706916166076,18526192807286106198,211694470334287787868
%N A381906 Expansion of (1/x) * Series_Reversion( x / ((1+x)^2 * B(x)) ), where B(x) is the g.f. of A001764.
%F A381906 G.f. A(x) satisfies A(x) = (1 + x*A(x))^2 * B(x*A(x)).
%F A381906 a(n) = Sum_{k=0..n} binomial(n+3*k+1,k) * binomial(2*n+2,n-k)/(n+3*k+1).
%o A381906 (PARI) a(n) = sum(k=0, n, binomial(n+3*k+1, k)*binomial(2*n+2, n-k)/(n+3*k+1));
%Y A381906 Cf. A381905, A381907.
%Y A381906 Cf. A001764, A381881.
%K A381906 nonn
%O A381906 0,2
%A A381906 _Seiichi Manyama_, Mar 10 2025