A217135 Numbers k such that 3^k - 8 is prime.

3, 4, 7, 8, 14, 20, 22, 62, 139, 254, 272, 430, 907, 1906, 2278, 2827, 3598, 6812, 15266, 20915, 26180, 26342, 27022, 48275, 65186, 69247, 86647

Offset: 1

Author

Vincenzo Librandi, Oct 01 2012

Keywords

• nonn

Comments

a(28) > 2*10^5. - Robert Price, Sep 02 2013

Crossrefs

Cf. A014224, A051783, A058958, A058959.

Programs

Mathematica

Select[Range[2, 5000], PrimeQ[3^# - 8] &]

PARI

for(n=2, 5*10^3, if(isprime(3^n-8), print1(n", ")))

Extensions

a(18)-a(27) from Robert Price, Sep 02 2013