A082400 - OEIS

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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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..54.

EXAMPLE

k = 5 gives 32 + 81 = 113, a prime.

MATHEMATICA

Do[p = 2^n + 3^(n-1); If[PrimeQ[p], Print[n]], {n, 1, 10^4}] (* Ryan Propper, Jul 23 2005 *)

PROG

(PARI) is(n)=ispseudoprime(2^n+3^(n-1)) \\ Charles R Greathouse IV, Jun 12 2017

CROSSREFS

Sequence in context: A319975 A307625 A165722 * A072993 A018444 A032378

Adjacent sequences: A082397 A082398 A082399 * A082401 A082402 A082403

KEYWORD

nonn

AUTHOR

Labos Elemer, Apr 14 2003

EXTENSIONS

a(37)-a(44) from Ryan Propper, Jul 23 2005

a(45)-a(54) from Michael S. Branicky, Jul 13 2023

STATUS

approved