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A231329
Numbers n such that (19^n + 4^n)/23 is prime.
0
7, 11, 211, 14461
OFFSET
1,1
COMMENTS
Conjecture: All terms are prime.
a(5) > 10^5.
MATHEMATICA
Select[ Prime[ Range[1, 100000] ], PrimeQ[ (19^# + 4^#)/23 ]& ]
PROG
(PARI) is(n)=ispseudoprime((19^n+4^n)/23) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
hard,nonn,more
AUTHOR
Robert Price, Nov 07 2013
STATUS
approved