OFFSET
1,2
EXAMPLE
a(8) = 54; a(8) = sigma_[8/1](1) + sigma_[8/2](2) + sigma_[8/4](4) + sigma_[8/8](8) = (1^8) + (1^4 + 2^4) + (1^2 + 2^2 + 4^2) + (1^1 + 2^1 + 4^1 + 8^1) = 54.
MATHEMATICA
a[n_] := DivisorSum[n, DivisorSigma[n/#, #] &]; Array[a, 50] (* Amiram Eldar, Oct 17 2021 *)
PROG
(PARI) a(n) = sumdiv(n, d, sigma(d, n/d)); \\ Michel Marcus, Oct 18 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Oct 16 2021
STATUS
approved