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A216420
Numbers k such that 13^k + k^13 - 1 is prime.
1
1, 5, 85, 155, 383, 6223
OFFSET
1,2
COMMENTS
a(7) > 2*10^5 if it exists. - Robert Price, Jul 07 2014
MATHEMATICA
Select[Range[0, 5000], PrimeQ[13^# + #^13 - 1] &]
PROG
(Magma) [n: n in [0..1000] | IsPrime(13^n+n^13-1)];
(PARI) is(n)=ispseudoprime(13^n+n^13-1) \\ Charles R Greathouse IV, Jun 13 2017
KEYWORD
nonn,hard,more
AUTHOR
Vincenzo Librandi, Sep 07 2012
EXTENSIONS
a(6) from Robert Price, May 24 2014
STATUS
approved