OFFSET
1,2
COMMENTS
If p is prime, a(p) = p * Sum_{p|p} lcm(p,p/p) / p = p * p/p = p.
EXAMPLE
a(18) = 18 * Sum_{p|18} lcm(p,18/p) / p = 18 * (lcm(2,9)/2 + lcm(3,6)/3) = 18 * (9 + 2) = 198.
MATHEMATICA
Table[n*Sum[(1/k) LCM[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