OFFSET
1,2
LINKS
K. Bringmann, J. Lovejoy, and R. Osburn, Rank and crank moments for overpartitions, Journal of Number Theory, 129 (2009), 1758-1772.
FORMULA
G.f.: (Product_{k>=1} (1+q^k)/(1-q^k)) * Sum_{n>=1} n*q^n/(1+q^n).
EXAMPLE
The 8 overpartitions of 8 are [3], [3'], [2,1], [2,1'], [2',1], [2',1'], [1,1,1], [1',1,1], and so a(3) = 10.
PROG
(PARI) my(N=44, q='q+O('q^N)); Vec( prod(k=1, N, (1+q^k)/(1-q^k)) * sum(k=1, N, k*q^k/(1+q^k)) ) \\ Joerg Arndt, Jun 18 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Jeremy Lovejoy, Jun 17 2020
STATUS
approved