A201363 - OEIS

%I #20 May 13 2023 01:44:31

%S 2,3,7,42066

%N Numbers k such that (2^k - k - 1)*2^k - 1 is prime.

%C No further terms less than 10000. - _T. D. Noe_, Nov 30 2011

%e 7 is in the sequence because (2^7 - 7 - 1)*2^7 - 1 = 15359 is prime.

%t lst={};Do[If[PrimeQ[(2^n - n-1)*2^n-1],AppendTo[lst,n]],{n,15000}];lst

%o (PARI) is(n)=ispseudoprime((2^n-n-1)<<n-1) \\ _Charles R Greathouse IV_, Feb 17 2017

%Y Cf. A201356, A201357, A201358, A201359, A201360, A201361, A201362.

%K nonn,hard,more

%O 1,1

%A _Michel Lagneau_, Nov 30 2011

%E a(4) from _Michael S. Branicky_, May 12 2023