OFFSET
1,1
COMMENTS
If k = p+1 where p is an odd prime, then k is a term. - Amiram Eldar, Sep 16 2024
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
phi(15) = 8, gcd(8, 14) = 2, 14 = 2*7, 2 prime factors.
MATHEMATICA
q[k_] := GCD[EulerPhi[k], k-1] == PrimeNu[k-1]; Select[Range[200], q] (* Amiram Eldar, Sep 16 2024 *)
PROG
(PARI) is(k) = k > 1 && gcd(eulerphi(k), k-1) == omega(k-1); \\ Amiram Eldar, Sep 16 2024
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved