OFFSET
0,2
FORMULA
a(n) = n+1+2*Sum_{k=1..n} Sum_{d^2|k} phi(d), where phi = Euler totient function A000010.
PROG
(PARI) a(n) = n + 1 + 2*sum(k=1, n, sumdiv(k, d, issquare(d)*eulerphi(sqrtint(d)))) \\ Michel Marcus, Jun 17 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladeta Jovovic, Sep 27 2001
STATUS
approved