A217385 Numbers n such that 9^n + 8 is prime.

1, 2, 4, 7, 10, 19, 22, 44, 62, 76, 122, 2191, 3134, 9244, 40999, 48230

Offset: 1

Author

Vincenzo Librandi, Oct 04 2012

Keywords

• nonn
• hard
• more

Comments

Contains exactly the halved even terms of A217136. - Bruno Berselli, Oct 04 2012

Crossrefs

Cf. A090649, A177093, A217136, A217384.

Programs

Mathematica

Select[Range[5000], PrimeQ[9^# + 8] &]

PARI

is(n)=ispseudoprime(9^n+8) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(14) from Bruno Berselli, Oct 05 2012

a(15)-a(16) derived from A217136 by Robert Price, May 19 2015