A082400 Numbers k such that 2^k + 3^(k-1) is prime.
1, 2, 3, 4, 5, 6, 7, 10, 12, 13, 16, 18, 23, 33, 34, 36, 37, 47, 48, 60, 64, 81, 102, 155, 160, 174, 222, 226, 237, 251, 282, 348, 790, 993, 1608, 1632, 1984, 2073, 3617, 3703, 5077, 5958, 6336, 8772, 10204, 10985, 12204, 12351, 13661, 14892, 29206, 30287, 33221, 34384
Offset: 1
Keywords
Examples
k = 5 gives 32 + 81 = 113, a prime.
Programs
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Mathematica
Do[p = 2^n + 3^(n-1); If[PrimeQ[p], Print[n]], {n, 1, 10^4}] (* Ryan Propper, Jul 23 2005 *) -
PARI
is(n)=ispseudoprime(2^n+3^(n-1)) \\ Charles R Greathouse IV, Jun 12 2017
Extensions
a(37)-a(44) from Ryan Propper, Jul 23 2005
a(45)-a(54) from Michael S. Branicky, Jul 13 2023