A215444 Numbers k such that 7^k + k^7 + 1 is prime.

0, 3, 5, 15, 375, 98003

Offset: 1

Author

Vincenzo Librandi, Sep 06 2012

Keywords

• nonn
• hard
• more

Comments

a(6) > 8000. - Joerg Arndt, Sep 29 2012

a(7) > 2*10^5. - Robert Price, Jun 15 2014

Crossrefs

Cf. A100357, A215441, A216423, A215442, A243934.

Programs

Magma

[k: k in [0..400] | IsPrime(7^k + k^7 + 1)];

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(6) from Robert Price, May 24 2014