A082103 Numbers n such that 3^n + 2^(n-1) is prime.

2, 3, 4, 6, 7, 8, 10, 15, 21, 24, 36, 49, 51, 86, 116, 134, 176, 284, 345, 498, 544, 649, 844, 1051, 1171, 1384, 1497, 1514, 1638, 1856, 2860, 2890, 3235, 3584, 4047, 5990, 7729, 8935, 9907, 15241, 15864, 17629, 19264, 28239, 43730, 46879, 65379, 89468, 128787, 139976

Offset

1,1

Comments

a(51) > 2*10^5. - Robert Price, May 06 2016

Links

Table of n, a(n) for n=1..50.

Example

n=4: 89 = 2*2*2 + 3*3*3*3 is prime.
n=15: 3^15 + 2^14 = 14365291 is prime.

Mathematica

Do[ If[ PrimeQ[3^n + 2^(n - 1)], Print[n]], {n, 7650}] (* Robert G. Wilson v, May 24 2004 *)
Select[Range[6000], PrimeQ[3^# + 2^(#-1)] &] (* Vincenzo Librandi, Mar 20 2015 *)

Prog

(Magma) [n: n in [0..1000] | IsPrime(3^n + 2^(n-1))]; // Vincenzo Librandi, Mar 20 2015
(PARI) is(n)=isprime(3^n+2^(n-1)) \\ Charles R Greathouse IV, Feb 17 2017

Crossrefs

Cf. A082101, A082102, A095906, A093717, A093793, A093765, A096185, A093794, A093795, A096186.

Sequence in context: A338031 A091199 A093452 * A219618 A328592 A175413

Adjacent sequences: A082100 A082101 A082102 * A082104 A082105 A082106

Keyword

nonn

Author

Labos Elemer, Apr 14 2003

Extensions

Edited and extended by Robert G. Wilson v, May 25 2004

Edited by N. J. A. Sloane, Sep 15 2008 at the suggestion of R. J. Mathar

a(37)-a(50) from Robert Price, May 06 2016

Status

approved