A186450 Primes of the form k! + 2^k - 1.

2, 5, 13, 151, 5167, 39918847

Offset

1,1

Comments

a(7) = 167! + 2^167 - 1 = 1503616514 ... 959365500927 has 301 digits ;

a(8) = 2609! + 2^2609 - 1 = 4110644622 ... 780469952511 has 7783 digits.

Links

Table of n, a(n) for n=1..6.

Example

for k=3, 13 is in the sequence because 3! + 2^3 - 1 = 13 is prime.

Mathematica

lst={}; Do[ q=k!+2^k-1; If[PrimeQ[q], AppendTo[lst, q]], {k, 0, 400}]; lst

Crossrefs

Cf. A186449.

Sequence in context: A230518 A241248 A275698 * A065797 A196273 A128772

Adjacent sequences: A186447 A186448 A186449 * A186451 A186452 A186453

Keyword

nonn

Author

Michel Lagneau, Feb 22 2011

Status

approved