OFFSET
1,2
COMMENTS
The PFGW program has been used to certify all the terms up to a(25), using a deterministic test which exploits the factorization of a(n)-1.
a(26) > 325000.
MATHEMATICA
Select[Range[1000], PrimeQ[Prime[#]* 2^# + 1] &]
PROG
(PARI) is(n, p=prime(n))=ispseudoprime(p<<n+1) \\ Charles R Greathouse IV, Jun 06 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Giovanni Resta, Mar 26 2014
STATUS
approved