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Numbers k such that 13^k + k^13 - 1 is prime.
1

%I #26 Sep 08 2022 08:46:03

%S 1,5,85,155,383,6223

%N Numbers k such that 13^k + k^13 - 1 is prime.

%C a(7) > 2*10^5 if it exists. - _Robert Price_, Jul 07 2014

%t Select[Range[0, 5000], PrimeQ[13^# + #^13 - 1] &]

%o (Magma) [n: n in [0..1000] | IsPrime(13^n+n^13-1)];

%o (PARI) is(n)=ispseudoprime(13^n+n^13-1) \\ _Charles R Greathouse IV_, Jun 13 2017

%Y Cf. A100357, A215434-A215437, A215439-A215445, A216375.

%K nonn,hard,more

%O 1,2

%A _Vincenzo Librandi_, Sep 07 2012

%E a(6) from _Robert Price_, May 24 2014