A215445 Numbers k such that 7^k + k^7 - 1 is prime.

1, 11, 65, 133, 679, 1571, 27517, 51631

Offset: 1

Author

Vincenzo Librandi, Sep 06 2012

Keywords

• nonn
• hard
• more

Comments

a(9) > 10^5. - Robert Price, Feb 23 2014

Crossrefs

Cf. A100357, A215434-A215444, A216375.

Programs

Mathematica

Select[Range[0, 5000], PrimeQ[7^# + #^7 - 1] &]

PARI

is(n)=ispseudoprime(7^n+n^7-1) \\ Charles R Greathouse IV, Jun 06 2017

Extensions

a(7)-a(8) from Robert Price, Feb 23 2014