OFFSET
1,1
COMMENTS
a(19) = 2255 is the least term that is not divisible by 3.
MATHEMATICA
f[n_] := Plus @@ DeleteDuplicates @ Map[EulerPhi, Divisors[n]]; m = 6000; Complement[Range[1, m, 2], Array[f, m^2]]
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Oct 03 2021
STATUS
approved