OFFSET
1,3
LINKS
Michel Marcus, Table of n, a(n) for n = 1..10000
MATHEMATICA
a[n_] := Plus @@ DivisorSigma[1, Floor[n/Select[Range[n], PrimeQ]]]; Array[a, 100] (* Amiram Eldar, Jul 05 2021 *)
PROG
(PARI) a(n) = my(s=0); forprime(p=2, n, s+=sigma(n\p)); s;
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Jul 05 2021
STATUS
approved