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A059747 Numbers k such that 3*2^k - 7 is prime. 0

%I #25 May 02 2023 03:21:37

%S 2,3,4,5,8,12,15,17,20,21,45,48,87,97,113,120,172,217,228,276,312,580,

%T 692,1132,1588,1668,2576,2591,3780,4311,4412,6205,11952,19897,19941,

%U 20525,22821,44757,62833

%N Numbers k such that 3*2^k - 7 is prime.

%C Next term > 12000. - _Vincenzo Librandi_, Sep 29 2012

%t Do[ If[ PrimeQ[ 3*2^n - 7 ], Print[n] ], {n, 3000} ]

%t Select[Range[6500], PrimeQ[(3*2^# - 7)] &] (* _Vincenzo Librandi_, Sep 29 2012 *)

%o (PARI) is(n)=ispseudoprime(3*2^n-7) \\ _Charles R Greathouse IV_, Jun 13 2017

%Y Cf. A059746.

%K nonn,more

%O 1,1

%A _Robert G. Wilson v_, Feb 10 2001

%E a(29)-a(32) from _Vincenzo Librandi_, Sep 29 2012

%E a(33) from _Bruno Berselli_, Sep 30 2012

%E a(34)-a(39) from _Michael S. Branicky_, May 01 2023

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Last modified March 28 05:39 EDT 2024. Contains 371235 sequences. (Running on oeis4.)