%I #23 Jul 12 2018 11:33:13

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

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

%C a(9) > 10^5. - _Robert Price_, Feb 23 2014

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

%o (PARI) is(n)=ispseudoprime(7^n+n^7-1) \\ _Charles R Greathouse IV_, Jun 06 2017

%Y Cf. A100357, A215434-A215444, A216375.

%K nonn,hard,more

%O 1,2

%A _Vincenzo Librandi_, Sep 06 2012

%E a(7)-a(8) from _Robert Price_, Feb 23 2014