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A128352
Numbers k such that (17^k - 5^k)/12 is prime.
19
5, 7, 17, 23, 43, 71, 239, 733, 1097
OFFSET
1,1
COMMENTS
All terms are primes.
a(10) > 10^5. - Robert Price, Jun 11 2013
MATHEMATICA
k=17; Do[p=Prime[n]; f=(k^p-5^p)/(k-5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]
PROG
(PARI) is(n)=isprime((17^n-5^n)/12) \\ Charles R Greathouse IV, Feb 17 2017
KEYWORD
nonn,hard,more
AUTHOR
Alexander Adamchuk, Feb 27 2007
STATUS
approved