OFFSET
0,3
EXAMPLE
A(x) = 1 + x*(1+x) + x^2*(1+x)*(1+3x) + x^3*(1+x)*(1+3x)*(1+6x) +...
PROG
(PARI) a(n)=polcoeff(sum(k=0, n, x^k*prod(j=0, k, 1+j*(j+1)/2*x+x*O(x^n))), n)
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Oct 28 2006
STATUS
approved