A128340 - OEIS
A128340
Numbers k such that (11^k + 5^k)/16 is prime.
20
7, 11, 181, 421, 2297, 2797, 4129, 4139, 7151, 29033
OFFSET
1,1
COMMENTS
All terms are primes.
a(11) > 10^5. - Robert Price, Feb 09 2013
MATHEMATICA
k=11; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]
PROG
(PARI) is(n)=isprime((11^n+5^n)/16) \\ Charles R Greathouse IV, Feb 17 2017
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, Feb 27 2007
EXTENSIONS
a(5)-a(10) from Robert Price, Feb 09 2013
STATUS
approved