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%I #11 Dec 15 2021 19:00:27
%S 2,5,11,13,331,599,18839,23747,24371,29339,32141,67421
%N Numbers k such that (11^k - 2^k)/9 is prime.
%C All terms are prime.
%C a(13) > 10^5.
%t Select[ Prime[ Range[1, 100000] ], PrimeQ[ (11^# - 2^#)/9 ]& ]
%o (PARI) is(n)=isprime((11^n-2^n)/9) \\ _Charles R Greathouse IV_, Feb 17 2017
%Y Cf. A004063, A028491, A057468, A059801, A121877, A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032.
%K hard,more,nonn
%O 1,1
%A _Robert Price_, Jan 25 2013