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A215445
Numbers k such that 7^k + k^7 - 1 is prime.
3
1, 11, 65, 133, 679, 1571, 27517, 51631
OFFSET
1,2
COMMENTS
a(9) > 10^5. - Robert Price, Feb 23 2014
MATHEMATICA
Select[Range[0, 5000], PrimeQ[7^# + #^7 - 1] &]
PROG
(PARI) is(n)=ispseudoprime(7^n+n^7-1) \\ Charles R Greathouse IV, Jun 06 2017
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Vincenzo Librandi, Sep 06 2012
EXTENSIONS
a(7)-a(8) from Robert Price, Feb 23 2014
STATUS
approved