OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..5000
FORMULA
a(n) = Sum_{d|n} phi(n/d) * d^(n/d-1).
If p is prime, a(p) = p.
MATHEMATICA
a[n_] := Sum[GCD[k, n]^(n/GCD[k, n] - 1), {k, 1, n}]; Array[a, 50] (* Amiram Eldar, Mar 12 2021 *)
PROG
(PARI) a(n) = sum(k=1, n, gcd(k, n)^(n/gcd(k, n)-1));
(PARI) a(n) = sumdiv(n, d, eulerphi(n/d)*d^(n/d-1));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Mar 12 2021
STATUS
approved