A248879 Numbers k >= 0 such that 2^k*(k+1)!+1 is prime.

0, 1, 3, 5, 8, 11, 16, 18, 25, 30, 36, 87, 118, 142, 2789, 3142, 3557, 3686, 4190, 7328

Offset: 1

Author

Robert Price, Mar 05 2015

Keywords

• nonn
• more

Comments

a(21) > 10^4.

Examples

			a(3) = 2^3*(3+1)!+1 = 193 which is prime.
		

Crossrefs

Cf. A093154.

Programs

Mathematica

Select[Range[0,10000], PrimeQ[2^#*(#+1)!+1] &]

PARI

for(n=0,10^3,if(ispseudoprime((n+1)!*2^n+1),print1(n,", "))) \\ Derek Orr, Mar 06 2015