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%I #16 Jan 17 2019 13:44:07
%S 1,2,32,43,973,1195,4471,5684,7988,46885
%N Numbers n such that 6*10^n + R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
%C Also numbers n such that (55*10^n+53)/9 is prime.
%C a(11) > 10^5. - _Robert Price_, Sep 07 2015
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/6/61117.htm#prime">Prime numbers of the form 611...117</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A101520(n) + 1.
%t Do[ If[ PrimeQ[(55*10^n + 53)/9], Print[n]], {n, 0, 10000}]
%Y Cf. A002275, A101520.
%K more,nonn
%O 1,2
%A _Robert G. Wilson v_, Jan 18 2005
%E a(10) from Erik Branger May 01 2013 by _Ray Chandler_, Aug 16 2013
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