OFFSET
1,2
COMMENTS
If p is prime, a(p) = Sum_{p|p} p * gcd(p,p/p) = p * 1 = p.
EXAMPLE
a(18) = Sum_{p|18} p * gcd(p,18/p) = 2*gcd(2,9) + 3*gcd(3,6) = 2*1 + 3*3 = 11.
MATHEMATICA
Table[Sum[k*GCD[k, n/k] (PrimePi[k] - PrimePi[k - 1]) (1 - Ceiling[n/k] + Floor[n/k]), {k, n}], {n, 100}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Jun 13 2021
STATUS
approved