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Numbers k such that 19*2^k+1 is prime.
2

%I #32 Oct 31 2020 04:49:29

%S 6,10,46,366,1246,2038,4386,4438,6838,7498,7998,9450,11890,17034,

%T 23290,73338,149146,323638,853546,2206266,6833086

%N Numbers k such that 19*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>

%o (PARI) is(n)=ispseudoprime(19*2^n+1) \\ _Charles R Greathouse IV_, Jun 06 2017

%K nonn,hard

%O 1,1

%A _James R. Buddenhagen_

%E Added more terms (from http://www.prothsearch.com/riesel1.html), _Joerg Arndt_, Apr 07 2013

%E a(21) from _Jeppe Stig Nielsen_, Oct 30 2020