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Numbers k such that 127*2^k+1 is prime.
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%I #30 Dec 23 2024 10:39:16

%S 2,12,18,24,54,72,114,180,214,504,558,964,1098,1420,2764,4322,5582,

%T 10538,14634,23970,61054,67318,88958,96744,297350,357840,376162,

%U 723530,916980,925012,1472718,1817862,5391378

%N Numbers k such that 127*2^k+1 is prime.

%H Ray Ballinger, <a href="http://www.prothsearch.com/index.html">Proth Search Page</a>

%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 Y. Gallot, <a href="http://www.utm.edu/research/primes/programs/gallot/index.html">Proth.exe: Windows Program for Finding Large Primes</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>

%t Select[Range[1000], PrimeQ[127*2^# + 1] & ] (* _Robert Price_, Dec 17 2018 *)

%o (PARI) is(n)=ispseudoprime(127*2^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017

%Y Cf. A032418.

%K nonn,more

%O 1,1

%A _James R. Buddenhagen_

%E a(25)-a(32) from the Ray Ballinger and Wilfrid Keller link by _Robert Price_, Dec 17 2018

%E a(33) from _Jeppe Stig Nielsen_, Dec 23 2024