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A215444
Numbers k such that 7^k + k^7 + 1 is prime.
3
0, 3, 5, 15, 375, 98003
OFFSET
1,2
COMMENTS
a(6) > 8000. - Joerg Arndt, Sep 29 2012
a(7) > 2*10^5. - Robert Price, Jun 15 2014
MATHEMATICA
Select[Range[0, 5000], PrimeQ[7^# + #^7 + 1] &]
PROG
(Magma) [n: n in [0..400] | IsPrime(7^n + n^7 + 1)]
(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(6) from Robert Price, May 24 2014
STATUS
approved