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A082103
Numbers n such that 3^n + 2^(n-1) is prime.
22
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
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
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