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A210506
Numbers k such that (11^k - 2^k)/9 is prime.
10
2, 5, 11, 13, 331, 599, 18839, 23747, 24371, 29339, 32141, 67421
OFFSET
1,1
COMMENTS
All terms are prime.
a(13) > 10^5.
MATHEMATICA
Select[ Prime[ Range[1, 100000] ], PrimeQ[ (11^# - 2^#)/9 ]& ]
PROG
(PARI) is(n)=isprime((11^n-2^n)/9) \\ Charles R Greathouse IV, Feb 17 2017
KEYWORD
hard,more,nonn
AUTHOR
Robert Price, Jan 25 2013
STATUS
approved