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A213216
Numbers n such that (12^n + 11^n)/23 is prime.
6
47, 401, 509, 8609
OFFSET
1,1
COMMENTS
All terms are prime.
a(5) > 10^5.
MATHEMATICA
Select[ Prime[ Range[1, 100000] ], PrimeQ[ (12^# + 11^#)/23 ]& ]
PROG
(PARI) is(n)=ispseudoprime((12^n+11^n)/23) \\ Charles R Greathouse IV, Feb 20 2017
CROSSREFS
KEYWORD
hard,nonn,more
AUTHOR
Robert Price, Mar 02 2013
EXTENSIONS
Removed incorrect first term of "2".
STATUS
approved