login
A128354
Numbers k such that (19^k - 5^k)/14 is prime.
19
5, 17, 31, 59, 373, 643, 2843, 5209, 85009
OFFSET
1,1
COMMENTS
All terms are primes.
a(10) > 10^5. - Robert Price, Jul 22 2013
MATHEMATICA
k=19; Do[p=Prime[n]; f=(k^p-5^p)/(k-5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]
PROG
(PARI) is(n)=isprime((19^n-5^n)/14) \\ Charles R Greathouse IV, Feb 17 2017
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, Feb 27 2007
EXTENSIONS
a(7)-a(9) from Robert Price, Jul 22 2013
STATUS
approved