OFFSET
1,2
COMMENTS
If p is prime, a(p) = Sum_{d|p} d^d * sopf(d) = 1^1*0 + p^p*p = p^(p+1).
EXAMPLE
a(4) = Sum_{d|4} d^d * sopf(d) = 1^1*sopf(1) + 2^2*sopf(2) + 4^4*sopf(4) = 0 + 8 + 512 = 520.
MATHEMATICA
Table[Sum[i^i*Sum[k (PrimePi[k] - PrimePi[k - 1]) (1 - Ceiling[i/k] + Floor[i/k]), {k, i}] (1 - Ceiling[n/i] + Floor[n/i]) , {i, n}], {n, 20}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, May 24 2021
STATUS
approved