A217355 Numbers k such that 8^k + 5 is prime.

1, 47, 91, 64655

Offset: 1

Author

Vincenzo Librandi, Oct 02 2012

Keywords

• nonn
• hard
• more

Comments

All terms are 1/3 of the terms of A059242 that are multiples of 3.

No more terms <= 10^5. - Tyler NeSmith

Crossrefs

Cf. A059242, A217354.

Programs

Magma

[n: n in [0..1000] | IsPrime(8^n + 5)];

Mathematica

Select[Range[1000], PrimeQ[8^# + 5] &]

PARI

is(n)=ispseudoprime(8^n+5) \\ Charles R Greathouse IV, Feb 20 2017

Extensions

a(4) from Tyler NeSmith, Jan 19 2021