A050865 - OEIS

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

%S 2,4,8,12,14,26,32,80,124,230,284,562,866,1830,2630,3122,3428,6278,

%T 9900,19888,20092,22706,29088,31412,44402,47914,53120,102330,135164,

%U 299306,345918

%N Numbers n such that 227*2^n-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 <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(227*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