login
Numbers n such that 43*2^n-1 is prime.
0

%I #20 Jan 17 2019 10:08:17

%S 7,31,67,251,767,1171,1643,25423,38863,50867,60391,100303,286171,

%T 399767

%N Numbers n such that 43*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(43*2^n-1) \\ _Charles R Greathouse IV_, Jun 13 2017

%Y Cf. A032371, 43*2^n+1 is prime.

%K hard,nonn

%O 1,1

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

%E More terms from _Hugo Pfoertner_, Oct 13 2004

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