OFFSET
1,1
COMMENTS
Fermat primes (A019434) are terms.
LINKS
Jaroslav Krizek, Table of n, a(n) for n = 1..200
EXAMPLE
Prime 17 is a term because gcd(sigma(16), phi(16)) = gcd(31, 8) = 1.
PROG
(Magma) [n: n in [1..10^6] | IsPrime(n) and GCD(SumOfDivisors(n-1), EulerPhi(n-1)) eq 1]
(PARI) isok(p) = isprime(p) && (gcd(eulerphi(p-1), sigma(p-1)) == 1); \\ Michel Marcus, Oct 06 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Jul 12 2016
STATUS
approved