OFFSET
1,3
COMMENTS
a(21) > 10^4.
EXAMPLE
a(3) = 2^3*(3+1)!+1 = 193 which is prime.
MATHEMATICA
Select[Range[0, 10000], PrimeQ[2^#*(#+1)!+1] &]
PROG
(PARI) for(n=0, 10^3, if(ispseudoprime((n+1)!*2^n+1), print1(n, ", "))) \\ Derek Orr, Mar 06 2015
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Mar 05 2015
STATUS
approved