A209405 G.f.: 1/(1-x) = Sum_{n>=0} a(n)*x^n*Product_{k=1..n+1} (1-x^k).

1, 2, 3, 6, 8, 15, 21, 34, 47, 74, 99, 151, 201, 287, 383, 540, 701, 970, 1255, 1688, 2171, 2882, 3657, 4801, 6058, 7819, 9816, 12566, 15619, 19826, 24540, 30812, 37950, 47319, 57901, 71769, 87435, 107525, 130482, 159660, 192721, 234633, 282240, 341656, 409549

Offset: 0

Author

Paul D. Hanna, Mar 08 2012

Keywords

• nonn

Examples

			G.f.: 1/(1-x) = 1*(1-x) + 2*x*(1-x)*(1-x^2) + 3*x^2*(1-x)*(1-x^2)*(1-x^3) + 6*x^3*(1-x)*(1-x^2)*(1-x^3)*(1-x^4) + 8*x^4*(1-x)*(1-x^2)*(1-x^3)*(1-x^4)*(1-x^5) +...
		

Crossrefs

Cf. A126796.

Programs

PARI

{a(n)=local(A=[1]); for(i=1,n+1, A=concat(A,0); A[#A]=1-polcoeff(sum(m=1, #A, A[m]*x^m*prod(k=1,m, 1-x^k +x*O(x^#A) )), #A) ); A[n+1]}
for(n=0,50,print1(a(n),", "))