OFFSET
1,4
LINKS
FORMULA
MATHEMATICA
f[p_, e_] := e*2^(PrimePi[p] - 1); q[1] = False; q[n_] := ! Divisible[Plus @@ f @@@ FactorInteger[n], 3]; a[n_] := DivisorSum[n, 1 &, q[#] &]; Array[a, 100] (* Amiram Eldar, Apr 15 2022 *)
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Apr 15 2022
STATUS
approved