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 A381939 #14 Mar 11 2025 07:56:10
%S A381939 1,4,13,74,568,4872,44576,425936,4199616,42404096,436238592,
%T A381939 4556085248,48179319808,514825553408,5550284218368,60296483084288,
%U A381939 659417378381824,7253858445852672,80209754567786496,891027699137609728,9939286070426992640,111286739309529858048
%N A381939 G.f. A(x) satisfies A(x) = (1 + x)^3 * B(x*A(x)), where B(x) is the g.f. of A001764.
%F A381939 a(n) = Sum_{k=0..n} binomial(4*k+1,k) * binomial(3*k+3,n-k)/(4*k+1).
%F A381939 a(n) = A367641(n) + A367641(n-1).
%o A381939 (PARI) a(n) = sum(k=0, n, binomial(4*k+1, k)*binomial(3*k+3, n-k)/(4*k+1));
%Y A381939 Cf. A366695, A381860, A381942.
%Y A381939 Cf. A001764, A367641.
%K A381939 nonn
%O A381939 0,2
%A A381939 _Seiichi Manyama_, Mar 10 2025