A381593 G.f. A(x) satisfies A(x) = 1/(1 - x * A(x) * A(x*A(x)))^2.
1, 2, 11, 88, 869, 9876, 124473, 1701630, 24870695, 384795184, 6257294780, 106377162620, 1882982975521, 34593496243070, 657935674477431, 12927331575084846, 261951066040220637, 5466177185459699916, 117315664923801661485, 2586804284853871362408
Offset: 0
Keywords
Programs
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PARI
a(n, k=2) = if(k==0, 0^n, k*sum(j=0, n, binomial(2*n+j+k, j)/(2*n+j+k)*a(n-j, 2*j)));