OFFSET
0,5
EXAMPLE
G.f.: A(x) = 1 + x + x^2 + x^3 + 2*x^4 + 3*x^5 + 6*x^6 + 9*x^7 +...
where:
A(x) = 1 + x/(1-x) + x^4/((1-x)*(1-x^2))^2 + x^9/((1-x)*(1-x^2)*(1-x^3))^3 + x^16/((1-x)*(1-x^2)*(1-x^3)*(1-x^4))^4 +...
PROG
(PARI) {a(n)=local(A=1); polcoeff(sum(m=0, n, x^(m^2)/prod(k=1, m, 1-x^k +x*O(x^n))^m), n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jul 17 2011
STATUS
approved