OFFSET
1,12
COMMENTS
Excess of sum of odd divisors of n that are < sqrt(n) over sum of even divisors of n that are < sqrt(n).
MATHEMATICA
nmax = 80; CoefficientList[Series[Sum[(-1)^(k + 1) k x^(k (k + 1))/(1 - x^k), {k, 1, nmax}], {x, 0, nmax}], x] // Rest
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Apr 05 2020
STATUS
approved