OFFSET
1,2
COMMENTS
Inverse Möbius transform of (-1)^phi(n) (which equals -1 if 1 <= n <= 2, and 1 if n >= 3).
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = A000005(n) - 3 - (-1)^n. - Robert Israel, Sep 13 2024
MAPLE
f:= proc(n) local d; add(q(d), d = numtheory:-divisors(n)) end proc:
map(f, [$1..100]); # Robert Israel, Sep 13 2024
MATHEMATICA
Table[DivisorSum[n, (-1)^EulerPhi[#] &], {n, 100}]
CROSSREFS
KEYWORD
sign
AUTHOR
Wesley Ivan Hurt, Jun 22 2024
STATUS
approved