OFFSET

1,1

COMMENTS

The first 5 known Fermat primes from A019434 are terms.

Conjecture: also primes p such that 2*phi(p-2) = p-1 (i.e., primes in A232720).

a(7) > 10^25. - Max Alekseyev, Feb 02 2024

PROG

(Magma) [n: n in [3..10000000] | IsPrime(n) and (n-1) mod EulerPhi(n-2) eq 0]

CROSSREFS

KEYWORD

nonn,more

AUTHOR

Jaroslav Krizek, Feb 25 2015

STATUS

approved