OFFSET
1,1
COMMENTS
Terms > 1871 correspond to probable primes.
Is 9 the only composite k such that (4^k - 2^k + 1)/3 is prime? Checked up to 20000. - Andrew Howroyd, Sep 10 2024
EXAMPLE
3 is a term because 3 is prime and (4^3 - 2^3 + 1)/3 = 19 is also prime.
PROG
(PARI) isok(k)={k%2 && ispseudoprime((4^k - 2^k + 1)/3)}
{ forprime(p=3, 2000, if(isok(p), print1(p, ", "))) } \\ Andrew Howroyd, Dec 31 2022
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Jorge Coveiro, Dec 31 2022
STATUS
approved