login
A201362
Numbers k such that (2^k - k - 1)*2^k + 1 is prime.
7
2, 7, 11, 13, 14, 20, 37, 53, 71, 132, 140, 613, 641, 665, 757, 788, 1878, 6774, 8777, 14575, 20917, 22352, 35828
OFFSET
1,1
EXAMPLE
2 is in the sequence because (2^2 - 2 - 1)*2^2 + 1 = 5 is prime.
MATHEMATICA
lst={}; Do[If[PrimeQ[(2^n - n-1)*2^n+1], AppendTo[lst, n]], {n, 10000}]; 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(20)-a(23) from Michael S. Branicky, Jul 12 2023
STATUS
approved