OFFSET
1,2
COMMENTS
A subset of odd values from A003306.
If p = 2*3^k + 1 is prime then p divides 2^(3^k) + (-1)^k, due to Euler's criterion.
LINKS
C. Caldwell's Prime Page for Divides Phi category.
PROG
(PARI) dp(n)=Mod(2, 2*3^n+1)^3^n==1;
forstep(n=1, 6225, 2, if(dp(n), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Serge Batalov, May 18 2020
STATUS
approved