A050855 - OEIS

%I #18 Jan 17 2019 10:08:17

%S 2,9,12,17,20,21,50,53,132,168,341,360,381,501,1065,1169,1545,2109,

%T 2520,2661,3149,4077,11252,21588,21692,39509,52685,67196,87708,232436,

%U 372312,417818,481385,507833

%N Numbers n such that 207*2^n-1 is prime.

%C Also in the sequence: 643478 - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

%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 <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>

%H Kosmaj, <a href="http://www.15k.org/riesellist.html">Riesel list k<300</a>.

%o (PARI) is(n)=ispseudoprime(207*2^n-1) \\ _Charles R Greathouse IV_, Jun 13 2017

%K hard,nonn

%O 1,1

%A _N. J. A. Sloane_, Dec 29 1999

%E More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008