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 A381615 #12 Mar 01 2025 22:48:10
%S A381615 1,1,4,31,320,3969,56080,876204,14860614,270231265,5223002719,
%T A381615 106613106181,2287120272173,51367948203527,1204141944566399,
%U A381615 29385603693050274,744943334951904519,19580887642660810193,532781828387893449124,14984377196395037979472
%N A381615 G.f. A(x) satisfies A(x) = 1/(1 - x * A(x*A(x)^3)^3).
%F A381615 Let a(n,k) = [x^n] A(x)^k.
%F A381615 a(n,0) = 0^n; a(n,k) = k * Sum_{j=0..n} binomial(3*n-2*j+k,j)/(3*n-2*j+k) * a(n-j,3*j).
%o A381615 (PARI) a(n, k=1) = if(k==0, 0^n, k*sum(j=0, n, binomial(3*n-2*j+k, j)/(3*n-2*j+k)*a(n-j, 3*j)));
%Y A381615 Cf. A088714, A381029.
%Y A381615 Cf. A120973, A212029, A381601.
%Y A381615 Cf. A381574.
%K A381615 nonn
%O A381615 0,3
%A A381615 _Seiichi Manyama_, Mar 01 2025