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A186449
Numbers k such that k! + 2^k - 1 is prime.
1
1, 2, 3, 5, 7, 11, 167, 2609, 6247, 7841
OFFSET
1,2
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
KEYWORD
nonn,more
AUTHOR
Michel Lagneau, Feb 22 2011
EXTENSIONS
a(9)-a(10) from Michael S. Branicky, May 03 2023
STATUS
approved