OFFSET
1,3
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..20000
FORMULA
Multiplicative with a(2^1) = -1, a(2^e) = 0 for e > 1, and a(p^e) = (p - 1)*p^(e-1) when p is an odd prime.
G.f.: Sum_{k>=1} mu(k)*x^k*(1 + x^(2*k))/(1 - x^(2*k))^2. - Ilya Gutkovskiy, Nov 02 2018
Dirichlet g.f.: zeta(s-1)*(1-2^(1-s))/zeta(s). - R. J. Mathar, Jan 07 2021
Sum_{k=1..n} a(k) ~ c * n^2, where c = 3/(2*Pi^2) = 0.151981... . - Amiram Eldar, Nov 12 2022
PROG
CROSSREFS
KEYWORD
sign,mult
AUTHOR
Antti Karttunen, Oct 31 2018
STATUS
approved