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A201363
Numbers k such that (2^k - k - 1)*2^k - 1 is prime.
7
2, 3, 7, 42066
OFFSET
1,1
COMMENTS
No further terms less than 10000. - T. D. Noe, Nov 30 2011
EXAMPLE
7 is in the sequence because (2^7 - 7 - 1)*2^7 - 1 = 15359 is prime.
MATHEMATICA
lst={}; Do[If[PrimeQ[(2^n - n-1)*2^n-1], AppendTo[lst, n]], {n, 15000}]; lst
PROG
(PARI) is(n)=ispseudoprime((2^n-n-1)<<n-1) \\ Charles R Greathouse IV, Feb 17 2017
KEYWORD
nonn,hard,more
AUTHOR
Michel Lagneau, Nov 30 2011
EXTENSIONS
a(4) from Michael S. Branicky, May 12 2023
STATUS
approved