%I #24 Jan 17 2019 10:08:17
%S 1,5,7,15,19,23,25,27,43,65,99,125,141,165,201,211,331,369,389,445,
%T 461,463,467,513,583,835,1071,1085,1107,1187,1197,1491,1513,2505,3859,
%U 3941,5989,9693,13125,17009,19459,33147,46433,51091,72813,105169,118531,153127
%N Numbers k such that 199*2^k-1 is prime.
%H Ray Ballinger and Wilfrid Keller, <a href="http://www.prothsearch.com/riesel1.html">List of primes k.2^n + 1 for k < 300</a>
%H Wilfrid Keller, <a href="http://www.prothsearch.com/riesel2.html">List of primes k.2^n - 1 for k < 300</a>
%H Kosmaj, <a href="http://www.15k.org/riesellist.html">Riesel list k<300</a>.
%H <a href="/index/Pri#riesel">Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime</a>
%t Select[Range[1000], PrimeQ[199*2^# - 1] & ] (* _Robert Price_, Dec 29 2018 *)
%o (PARI) is(n)=ispseudoprime(199*2^n-1) \\ _Charles R Greathouse IV_, Jun 13 2017
%K hard,nonn
%O 1,2
%A _N. J. A. Sloane_, Dec 29 1999
%E More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
%E a(48) from the Wilfrid Keller link by _Robert Price_, Dec 29 2018