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A128336
Numbers k such that (6^k + 5^k)/11 is prime.
26
3, 5, 17, 397, 409, 643, 1783, 2617, 4583, 8783
OFFSET
1,1
COMMENTS
All terms are primes.
No other terms less than 100000. - Robert Price, May 11 2012
MATHEMATICA
k=6; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]
PROG
(PARI) forprime(p=3, 1e4, if(ispseudoprime((6^p+5^p)/11), print1(p", "))) \\ Charles R Greathouse IV, Jul 16 2011
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, Feb 27 2007
EXTENSIONS
a(7)-a(9) from Alexander Adamchuk, May 04 2010
One more term (8783) added (unknown discoverer) corresponding to a probable prime with 6834 digits by Jean-Louis Charton, Oct 06 2010
STATUS
approved