A118805 G.f.: 1 = Sum_{n>=0} a(n)*x^n*Product_{k=1..n} (1-k*x)^2.

1, 2, 11, 106, 1506, 28736, 694719, 20452602, 712529978, 28746803264, 1320665162746, 68164569542628, 3909330000805268, 246855506805662816, 17030177827550184395, 1275139722566251183642, 103032621304705343054010

Offset: 0

Author

Paul D. Hanna, May 02 2006

Keywords

• nonn

Examples

			1 = 1*(1-x)^2 + 2*x*((1-x)(1-2x))^2 + 11*x^2*((1-x)(1-2x)(1-3x))^2 + ... + a(n)*x^n*((1-x)(1-2x)(1-3x)...(1-n*x))^2 + ...
		

Links

• Vaclav Kotesovec, Table of n, a(n) for n = 0..32

Crossrefs

Cf. A118804 (variant).

Programs

PARI

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