OFFSET
0,4
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..250
EXAMPLE
G.f.: A(x) = 1 + x + x^2 + 2*x^3 + 3*x^4 + 6*x^5 + 12*x^6 + 25*x^7 +...
where A(x) = 1 + x/(1-x) + x^3/((1-2*x)*(1-x^2)) + x^6/((1-3*x)*(1-2*x^2)*(1-x^3)) + x^10/((1-4*x)*(1-3*x^2)*(1-2*x^3)*(1-x^4)) +...
PROG
(PARI) {a(n)=polcoeff(1+sum(m=1, n, x^(m*(m+1)/2)/prod(k=1, m, 1-(m-k+1)*x^k+x*O(x^n))), n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jan 20 2012
STATUS
approved