OFFSET
1,2
COMMENTS
See comments and references in A019269, which gives the number of iterations needed to reach a(n).
MATHEMATICA
psi[1] = 1; psi[n_] := n * Times @@ (1 + 1/Transpose[FactorInteger[n]][[1]]); a[n_] := NestWhile[psi, n, FactorInteger[#][[-1, 1]] > 3 &]; Array[a, 100] (* Amiram Eldar, Aug 31 2021 *)
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Aug 31 2021
STATUS
approved