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Numbers n such that 123*2^n-1 is prime.
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%I #18 Jan 17 2019 10:08:17

%S 2,3,11,15,23,24,27,35,71,84,108,122,123,138,236,242,290,392,500,611,

%T 747,771,1106,1490,3560,5111,6066,8660,8927,19451,19730,28316,30471,

%U 49515,93762,117083,168435,206663,249242,255402,261530,355727,389052,516456,518540,521031

%N Numbers n such that 123*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(123*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