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%I #21 Sep 08 2022 08:45:16
%S 2,3,5,11,12,23,75,101,122,173,647,2015,2684,11700,19625
%N Numbers n such that 6*10^n + R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
%C Also numbers n such that (55*10^n+17)/9 is prime.
%C a(16) > 10^5 - _Robert Price_, Sep 09 2015
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/6/61113.htm#prime">Prime numbers of the form 611...113</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A101519(n) + 1.
%t Do[ If[ PrimeQ[(55*10^n + 17)/9], Print[n]], {n, 0, 10000}]
%t Select[Range[0, 10000], PrimeQ[(55 10^# + 17)/9] &] (* _Vincenzo Librandi_, Sep 10 2015 *)
%o (Magma) [n: n in [0..500]| IsPrime((55*10^n + 17) div 9)]; // _Vincenzo Librandi_, Sep 10 2015
%Y Cf. A002275, A101519.
%K more,nonn
%O 1,1
%A _Robert G. Wilson v_, Jan 18 2005
%E Addition of a(14)-a(15) from Kamada data by _Robert Price_, Dec 12 2010
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