OFFSET
1,2
COMMENTS
If p is prime, a(p) = Sum_{d|p} d^gcd(d,p/d) = 1^1 + p^1 = p + 1.
EXAMPLE
a(8) = Sum_{d|8} d^gcd(d,8/d) = 1^1 + 2^2 + 4^2 + 8^1 = 29.
MATHEMATICA
Table[Sum[k^GCD[k, n/k] (1 - Ceiling[n/k] + Floor[n/k]), {k, n}], {n, 80}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, May 19 2021
STATUS
approved