OFFSET
1,2
COMMENTS
It can be shown that this is a subsequence of A028982.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MATHEMATICA
Select[Range[3490], CoprimeQ[DivisorSigma[1, #], DivisorSigma[0, #]] &] (* Jayanta Basu, Jun 27 2013 *)
PROG
(PARI) isok(n) = gcd(sigma(n), numdiv(n)) == 1; \\ Michel Marcus, Sep 24 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved