A186449 Numbers k such that k! + 2^k - 1 is prime.

1, 2, 3, 5, 7, 11, 167, 2609, 6247, 7841

Offset

1,2

Links

Table of n, a(n) for n=1..10.

Example

7! + 2^7 - 1 = 5167 is prime, therefore 7 is in the sequence.
11! + 2^11 - 1 = 39918847 is prime, therefore 11 is in the sequence.
2609! + 2^2609 - 1 = 4110644622026.....780469952511 (7783 digits) is prime, therefore 2609 is in the sequence.

Mathematica

lst={}; Do[If[PrimeQ[k!+2^k-1], AppendTo[lst, k]], {k, 3000}]; lst

Prog

(Magma) [ n: n in [0..167] | IsPrime(Factorial(n)+2^n-1) ]; // Klaus Brockhaus, Feb 22 2011
(PARI) is(n)=ispseudoprime(n!+2^n-1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A186450.

Sequence in context: A185267 A088249 A241724 * A046480 A235000 A067906

Adjacent sequences: A186446 A186447 A186448 * A186450 A186451 A186452

Keyword

nonn,more

Author

Michel Lagneau, Feb 22 2011

Extensions

a(9)-a(10) from Michael S. Branicky, May 03 2023

Status

approved