A082103 - OEIS

%I #22 Sep 08 2022 08:45:09

%S 2,3,4,6,7,8,10,15,21,24,36,49,51,86,116,134,176,284,345,498,544,649,

%T 844,1051,1171,1384,1497,1514,1638,1856,2860,2890,3235,3584,4047,5990,

%U 7729,8935,9907,15241,15864,17629,19264,28239,43730,46879,65379,89468,128787,139976

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

%C a(51) > 2*10^5. - _Robert Price_, May 06 2016

%e n=4: 89 = 2*2*2 + 3*3*3*3 is prime.

%e n=15: 3^15 + 2^14 = 14365291 is prime.

%t Do[ If[ PrimeQ[3^n + 2^(n - 1)], Print[n]], {n, 7650}] (* _Robert G. Wilson v_, May 24 2004 *)

%t Select[Range[6000], PrimeQ[3^# + 2^(#-1)] &] (* _Vincenzo Librandi_, Mar 20 2015 *)

%o (Magma) [n: n in [0..1000] | IsPrime(3^n + 2^(n-1))]; // _Vincenzo Librandi_, Mar 20 2015

%o (PARI) is(n)=isprime(3^n+2^(n-1)) \\ _Charles R Greathouse IV_, Feb 17 2017

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

%K nonn

%O 1,1

%A _Labos Elemer_, Apr 14 2003

%E Edited and extended by _Robert G. Wilson v_, May 25 2004

%E Edited by _N. J. A. Sloane_, Sep 15 2008 at the suggestion of _R. J. Mathar_

%E a(37)-a(50) from _Robert Price_, May 06 2016