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 A120973 #10 Mar 01 2025 08:35:51
%S A120973 1,1,6,60,776,11802,201465,3759100,75404151,1608036861,36172106112,
%T A120973 853346084343,21021015647574,538868533164995,14336235065928966,
%U A120973 394957784033440194,11246848201518516044,330520280036501809758
%N A120973 G.f. A(x) satisfies A(x) = 1 + x*A(x)^3 * A(x*A(x)^3)^3.
%F A120973 G.f. A(x) satisfies: A(x) = G(G(x)-1), A(G(x)-1) = G(A(x)-1), A(x) = G(x*A(x)^3) and A(x/G(x)^3) = G(x), where G(x) is the g.f. of A120972 and satisfies G(x/G(x)^3) = 1 + x.
%F A120973 From _Seiichi Manyama_, Mar 01 2025: (Start)
%F A120973 Let a(n,k) = [x^n] A(x)^k.
%F A120973 a(n,0) = 0^n; a(n,k) = k * Sum_{j=0..n} binomial(3*n+k,j)/(3*n+k) * a(n-j,3*j). (End)
%o A120973 (PARI) {a(n)=local(A,G=[1,1]);for(i=1,n,G=concat(G,0); G[ #G]=-Vec(subst(Ser(G),x,x/Ser(G)^3))[ #G]); A=Vec(((Ser(G)-1)/x)^(1/3));A[n+1]}
%o A120973 (PARI) a(n, k=1) = if(k==0, 0^n, k*sum(j=0, n, binomial(3*n+k, j)/(3*n+k)*a(n-j, 3*j))); \\ _Seiichi Manyama_, Mar 01 2025
%Y A120973 Cf. A120972; variants: A110447, A120971, A120975, A120977.
%K A120973 nonn
%O A120973 0,3
%A A120973 _Paul D. Hanna_, Jul 20 2006