A381572 G.f. A(x) satisfies A(x) = 1/(1 - x*A(x*A(x)))^2.

1, 2, 7, 38, 267, 2232, 21200, 222556, 2536661, 31010886, 403097573, 5535291884, 79900803514, 1207657432714, 19052200105025, 312909670649562, 5338325737985841, 94422672774323512, 1728653714036740230, 32708138881741705812, 638762549199936808759, 12859693257887577375744

Offset

0,2

Links

Table of n, a(n) for n=0..21.

Formula

See A381571.

G.f.: B(x)^2, where B(x) is the g.f. of A381029.

Prog

(PARI) a(n, k=1) = if(k==0, 0^n, 2*k*sum(j=0, n, binomial(2*n-j+2*k, j)/(2*n-j+2*k)*a(n-j, j)));

Crossrefs

Column k=1 of A381571.

Cf. A381029.

Sequence in context: A209006 A168492 A346646 * A032109 A368232 A337026

Adjacent sequences: A381569 A381570 A381571 * A381573 A381574 A381575

Keyword

nonn,new

Author

Seiichi Manyama, Feb 28 2025

Status

approved