|
%I #16 Nov 14 2019 17:16:22
%S 4,10,14,16,26,50,56,70,116,2072,6250,13670,14216,14626,396128
%N Numbers k such that A000295(k) = 2^k-k-1 is prime.
%C The next term is > 400000.
%C Equals A063791 + 1. - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008
%C Some of the results were computed using the PrimeFormGW (PFGW) primality-testing program. - _Hugo Pfoertner_, Nov 14 2019
%e a(1) = 4 because 2^4 - 4 - 1 = 11 is prime.
%Y Cf. A000295 (2^n-n-1), A099440 (primes in A000295), A099441 (2^n-n-1 is a semiprime), A099442 (semiprimes in A000295).
%K nonn,more,hard
%O 1,1
%A _Hugo Pfoertner_, Oct 18 2004
%E a(15) (a PRP) from _Karsten Bonath_, Jun 07 2018
|
