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
Keywords
Examples
n=4: 89 = 2*2*2 + 3*3*3*3 is prime. n=15: 3^15 + 2^14 = 14365291 is prime.
Crossrefs
Programs
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Magma
[n: n in [0..1000] | IsPrime(3^n + 2^(n-1))]; // Vincenzo Librandi, Mar 20 2015
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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 *) -
PARI
is(n)=isprime(3^n+2^(n-1)) \\ Charles R Greathouse IV, Feb 17 2017
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
Comments