A124462 Row 2 of rectangular table A124460.
1, 3, 8, 23, 73, 251, 919, 3549, 14371, 60720, 266481, 1209807, 5662008, 27238884, 134391046, 678739990, 3503708942, 18462855900, 99211177417, 543161148837, 3027439667989, 17167987227428, 98995692542858, 580166879766649
Offset: 0
Keywords
Programs
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PARI
{a(n)=local(m=max(n,2),R=vector(m+1,r,vector(m+1,c,binomial(r+c-2,c-1)))); for(i=0,m,for(r=0,m,R[r+1]=Vec(sum(c=0,m,x^c*Ser(R[c+1])^r+O(x^(m+1))))));R[3][n+1]}
Formula
G.f.: A(x) = Sum_{n>=0} x^n*R_n(x)^2, where R_n(x) is the g.f. of row n in table A124460 and satisfies: R_n(x) = Sum_{k>=0} x^k * R_k(x)^n for n>=0.