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%I #20 Sep 08 2022 08:46:11
%S 3,7,13,15,21,73,231,301,493,895,955,4069,5057,5415,15325,19845,21603,
%T 24577,37877,40193,44283
%N Numbers k such that 4^k - 2^k - 3 is prime.
%C a(22) > 150000. - _Hans Havermann_, Jul 18 2015
%e 3 is in this sequence because 4^3 - 2^3 - 3 = 53.
%t Select[Range[15000], PrimeQ[4^# - 2^# - 3] &]
%o (Magma) [n: n in [1..800] | IsPrime(4^n-2^n-3)];
%o (PARI) for(n=1,500,if(ispseudoprime(4^n-2^n-3),print1(n,", "))) \\ _Derek Orr_, Mar 03 2015
%Y Cf. A098845.
%K nonn,more
%O 1,1
%A _Vincenzo Librandi_, Mar 02 2015
%E a(15)-a(21) from _Hans Havermann_, Jul 18 2015
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