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 A381907 #10 Mar 10 2025 06:59:29
%S A381907 1,4,25,197,1783,17646,185622,2039617,23149542,269367631,3196544816,
%T A381907 38539697456,470773651286,5813914938293,72470441063067,
%U A381907 910587733474165,11521140613913305,146659482494039073,1876975898990490298,24137070792680577688,311724732112458291945
%N A381907 Expansion of (1/x) * Series_Reversion( x / ((1+x)^3 * B(x)) ), where B(x) is the g.f. of A001764.
%F A381907 G.f. A(x) satisfies A(x) = (1 + x*A(x))^3 * B(x*A(x)).
%F A381907 a(n) = Sum_{k=0..n} binomial(n+3*k+1,k) * binomial(3*n+3,n-k)/(n+3*k+1).
%o A381907 (PARI) a(n) = sum(k=0, n, binomial(n+3*k+1, k)*binomial(3*n+3, n-k)/(n+3*k+1));
%Y A381907 Cf. A381905, A381906.
%Y A381907 Cf. A001764, A381882.
%K A381907 nonn
%O A381907 0,2
%A A381907 _Seiichi Manyama_, Mar 10 2025