A185758 A diagonal of triangle A185755.

2, 15, 120, 1190, 14595, 215950, 3761310, 75550188, 1721103648, 43872089118, 1237592664451, 38282002057156, 1288537309627464, 46886217384094764, 1834003542264708444, 76744318019878844916, 3420833746251201921980

Offset

1,1

Comments

A185755(n,k) equals the coefficient of x^n*y^k in the n-th iteration of x*(1+xy)/(1-x).

Links

Table of n, a(n) for n=1..17.

Prog

 (PARI) {a(n)=local(A=x, G=x*(1+x*y)/(1-x)); for(i=1, n+1, A=subst(G, x, A+O(x^(n+2)))); polcoeff(polcoeff(A, n+1, x), n-1, y)}

Crossrefs

Cf. A185755, A185756, A185757, A185759.

Sequence in context: A369203 A074621 A341929 * A052448 A168502 A369108

Adjacent sequences: A185755 A185756 A185757 * A185759 A185760 A185761

Keyword

nonn

Author

Paul D. Hanna, Feb 03 2011

Status

approved