OFFSET
1,2
COMMENTS
These are Williams primes to base 3.
Half of the even terms of A002235.
LINKS
H. C. Williams, The primality of certain integers of the form 2Ar^n - 1, Acta Arith. 39 (1981), 7-17.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[3*4^# - 1] &]
PROG
(PARI) for(n=1, 10000, if(isprime(3*4^n-1), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Tim Johannes Ohrtmann, Apr 19 2016
EXTENSIONS
a(25) corrected and a(33)-a(36) added by Giovanni Resta, Apr 19 2016, using data from A002235.
STATUS
approved