OFFSET
1,2
COMMENTS
The sequence appears to be infinite, but I have no proof.
LINKS
Dumitru Damian, Table of n, a(n) for n = 1..10000
EXAMPLE
35 is a term since 1 + phi(35)^4 = 1 + 24^4 = 331777 is prime.
MATHEMATICA
Select[Range[200], PrimeQ[1+EulerPhi[#]^4]&] (* Harvey P. Dale, Jul 22 2022 *)
PROG
(Python)
from sympy import isprime, totient
print([n for n in range(1, 10**3) if isprime(1+totient(n)**4)]) # Dumitru Damian, Jan 29 2022
(PARI) isok(k) = isprime(1+eulerphi(k)^4); \\ Michel Marcus, Jan 30 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Carmine Suriano, Sep 14 2010
STATUS
approved