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A186450
Primes of the form k! + 2^k - 1.
2
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.
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
KEYWORD
nonn
AUTHOR
Michel Lagneau, Feb 22 2011
STATUS
approved