OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = Sum_{d|n} (-1)^(n-d) * binomial(n/d,d).
a(p) = p, where p is odd prime.
MATHEMATICA
nmax = 60; CoefficientList[Series[Sum[((1 - (-x)^k)^k - 1), {k, 1, nmax}], {x, 0, nmax}], x] // Rest
Table[DivisorSum[n, (-1)^(n - #) Binomial[n/#, #] &], {n, 1, 60}]
PROG
(PARI) a(n)={sumdiv(n, d, (-1)^(n-d) * binomial(n/d, d))} \\ Andrew Howroyd, Sep 14 2019
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Sep 14 2019
STATUS
approved