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A187805
Numbers n such that (7^n + 6^n)/13 is prime.
7
3, 53, 83, 487, 743
OFFSET
1,1
COMMENTS
All terms are prime.
a(6) > 10^5
MATHEMATICA
Select[ Prime[ Range[100000] ], PrimeQ[ (7^# + 6^#)/13 ]& ]
PROG
(PARI) is(n)=ispseudoprime((7^n+6^n)/13) \\ Charles R Greathouse IV, Feb 17 2017
CROSSREFS
KEYWORD
more,hard,nonn
AUTHOR
Robert Price, Jan 06 2013
STATUS
approved