A201362 - OEIS

%I #12 Jul 12 2023 13:02:44

%S 2,7,11,13,14,20,37,53,71,132,140,613,641,665,757,788,1878,6774,8777,

%T 14575,20917,22352,35828

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

%e 2 is in the sequence because (2^2 - 2 - 1)*2^2 + 1 = 5 is prime.

%t lst={};Do[If[PrimeQ[(2^n - n-1)*2^n+1],AppendTo[lst,n]],{n,10000}];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,  A201363.

%K nonn,hard,more

%O 1,1

%A _Michel Lagneau_, Nov 30 2011

%E a(20)-a(23) from _Michael S. Branicky_, Jul 12 2023