OFFSET
0,3
COMMENTS
Here sigma(n) equals the sum of divisors of n (A000203).
LINKS
Paul D. Hanna, Table of n, a(n) for n = 0..720
EXAMPLE
G.f.: A(x) = 1 + x + 2*x^2 + 5*x^3 + 12*x^4 + 29*x^5 + 71*x^6 + 175*x^7 +...
where
A(x) = 1 + x/(1-x) + x^2/(1-x)^3 + x^3/(1-x)^4 + x^4/(1-x)^7 + x^5/(1-x)^6 + x^6/(1-x)^12 + x^7/(1-x)^8 + x^8/(1-x)^15 + x^9/(1-x)^13 + x^10/(1-x)^18 +...
PROG
(PARI) {a(n)=polcoeff(1+sum(m=1, n, x^m/(1-x+x*O(x^n))^sigma(m)), n)}
for(n=0, 40, print1(a(n), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jul 03 2013
STATUS
approved