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%I #11 Sep 08 2022 08:45:31
%S 5,6,7,9,11,12,13,16,17,18,19,20,21,22,23,25,27,28,29,30,31,32,33,34,
%T 35,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,
%U 59,60,61,62,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83
%N Numbers k such that 3^k + 2 is not prime.
%t a = {}; c = 3^x + 2; Do[If[PrimeQ[c],0, AppendTo[a, x]], {x, 0, 100}]; a
%t Select[Range[90],CompositeQ[3^#+2]&] (* _Harvey P. Dale_, Sep 25 2021 *)
%o (Magma) [n: n in [0..100]| not IsPrime(3^n+2)] // _Vincenzo Librandi_, Jan 28 2011
%Y Cf. A057735, A051783.
%K nonn
%O 1,1
%A _Artur Jasinski_, Sep 03 2007
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