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A050559 Numbers k such that 67*2^k-1 is prime. 0

%I

%S 5,9,21,45,65,77,273,677,1049,1721,17105,18645,27761,61661,79773,

%T 403461,527037,722805

%N Numbers k such that 67*2^k-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 Kosmaj, <a href="http://www.15k.org/riesellist.html">Riesel list 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[67*2^# - 1] & ] (* _Robert Price_, Dec 22 2018 *)

%o (PARI) is(n)=ispseudoprime(67*2^n-1) \\ _Charles R Greathouse IV_, Jun 13 2017

%K hard,nonn,more

%O 1,1

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

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

%E a(18) from the Wilfrid Keller link by _Robert Price_, Dec 22 2018

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Last modified October 21 20:44 EDT 2019. Contains 328315 sequences. (Running on oeis4.)