A132829 Numbers k such that 3^k + 2 is not prime.

5, 6, 7, 9, 11, 12, 13, 16, 17, 18, 19, 20, 21, 22, 23, 25, 27, 28, 29, 30, 31, 32, 33, 34, 35, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83

Offset: 1

Author

Artur Jasinski, Sep 03 2007

Keywords

• nonn

Crossrefs

Cf. A057735, A051783.

Programs

Magma

[n: n in [0..100]| not IsPrime(3^n+2)]; // Vincenzo Librandi, Jan 28 2011

Mathematica

a = {}; c = 3^x + 2; Do[If[PrimeQ[c],0, AppendTo[a, x]], {x, 0, 100}]; a
Select[Range[90],CompositeQ[3^#+2]&] (* Harvey P. Dale, Sep 25 2021 *)