A145106 Numbers n such that 6^n+5 is prime.

1, 2, 4, 7, 10, 14, 18, 32, 55, 102, 177, 190, 247, 276, 372, 1524, 1545, 2502, 4966, 5294, 13030, 13785, 14329, 27333, 44224, 93812, 127176, 128640, 136434, 184614, 269407, 311257, 349903, 389756

Offset: 1

Author

Dmitry Kamenetsky, Oct 02 2008

Keywords

• nonn

Comments

a(27) > 10^5. - Robert Price, Aug 06 2017

As reported by Lelio R Paula in November 2014 at primenumbers.net/prptop, the following three terms are also in this sequence: 127176, 128640, 136434. It is not confirmed that they are the next terms, however. - Robert Price, Aug 06 2017

Examples

			6^1+5=11 and 6^2+5=41, which are both prime, so 1 and 2 are in the sequence. 6^3+5=221 is not prime since it is divisible by 7, so 3 is not in the sequence.
		

Crossrefs

Cf. A059614.

Programs

Mathematica

Select[Range[0, 100000], PrimeQ[6^# + 5] &] (* Robert Price, Aug 06 2017 *)

PARI

is(n)=ispseudoprime(6^n+5) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(21)-a(26) from Robert Price, Aug 06 2017

a(27)-a(30) from Paul Bourdelais, Jan 28 2021

a(31)-a(34) from Paul Bourdelais, Feb 11 2021