A126267 A diagonal of triangle A126265: a(n) = A126265(n+2,n).

1, 6, 24, 140, 1320, 12432, 121072, 1420848, 19012320, 267512300, 4002574224, 64842612276, 1121345413552, 20409576486600, 390729145716480, 7869294632279648, 166020221631955680, 3654120873937484628

Offset

0,2

Comments

a(n) is divisible by (n+1)*(n+2)/2. Rows of triangle A126265 lists coefficients of q in e.g.f. that satisfies: W(x,q) = exp( q*x*W(q*x,q) ).

Links

Table of n, a(n) for n=0..17.

Prog

(PARI) {a(n)=local(W=x); for(i=1, n+2, W=x*exp(subst(W, x, q*x+x*O(x^(n+2))))); if(n<0, 0, Vec(Vec(W)[n+3]*(n+2)!+q*O(q^((n+2)*(n+3)/2)))[n+1])}

Crossrefs

Cf. A126265, A126266.

Sequence in context: A110707 A047712 A188330 * A026947 A366757 A250743

Adjacent sequences: A126264 A126265 A126266 * A126268 A126269 A126270

Keyword

nonn

Author

Paul D. Hanna, Dec 22 2006

Status

approved