A107881 Column 0 of triangle A107880.

1, 2, 3, 7, 26, 141, 1034, 9693, 111522, 1528112, 24372513, 444461496, 9135985760, 209223309377, 5286985099830, 146225910921737, 4395973641599418, 142794782804641965, 4985911547339049132, 186284207595651780174

Offset: 0

Author

Paul D. Hanna, Jun 04 2005

Keywords

• nonn

Examples

			1 = 1*(1-x)^2 + 2*x*(1-x)^2 + 3*x^2*(1-x)^3 +
7*x^3*(1-x)^5 + 26*x^4*(1-x)^8 + 141*x^5*(1-x)^12 +...
		

Crossrefs

Cf. A107880, A107882, A107883.

Programs

PARI

{a(n)=polcoeff(1-sum(k=0,n-1,a(k)*x^k*(1-x+x*O(x^n))^(2+k*(k-1)/2)),n)}

Formula

G.f.: 1 = Sum_{k>=0} a(k)*x^k*(1-x)^(2 + k*(k-1)/2).