OFFSET
1,9
COMMENTS
Number of odd proper divisors of n minus number of even proper divisors of n.
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
FORMULA
MATHEMATICA
nmax = 80; CoefficientList[Series[Sum[(-1)^(k + 1) x^(2 k)/(1 - x^k), {k, 1, nmax}], {x, 0, nmax}], x] // Rest
Table[-DivisorSum[n, (-1)^# &, # < n &], {n, 1, 80}]
PROG
(PARI) A325937(n) = -sumdiv(n, d, if(d==n, 0, ((-1)^d))); \\ Antti Karttunen, Sep 20 2019
CROSSREFS
KEYWORD
sign,look
AUTHOR
Ilya Gutkovskiy, Sep 09 2019
STATUS
approved