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

1,3

Comments

a(21) > 10^4.

Links

Table of n, a(n) for n=1..20.

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

Cf. A093154.

Sequence in context: A340318 A175489 A289244 * A014688 A167136 A099836

Adjacent sequences: A248876 A248877 A248878 * A248880 A248881 A248882

Keyword

nonn,more

Author

Robert Price, Mar 05 2015

Status

approved