OFFSET
1,1
LINKS
Ray Ballinger and Wilfrid Keller, List of primes k.2^n + 1 for k < 300
Wilfrid Keller, List of primes k.2^n - 1 for k < 300
Kosmaj, Riesel list k<300.
MATHEMATICA
b=81; i=0; Table[While[i++; cp=b*2^i-1; !PrimeQ[cp]]; i, {j, 1, 17}]
PROG
(PARI) is(n)=ispseudoprime(81*2^n-1) \\ Charles R Greathouse IV, Feb 20 2017
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
N. J. A. Sloane, Dec 29 1999
EXTENSIONS
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
Lei Zhou, Nov 08 2013, added a Mathematica program for small elements.
STATUS
approved