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%I #16 Jan 17 2019 13:44:07
%S 2,260,417,953,2138,2969,3045,11777,23648
%N Numbers n such that 6*10^n + R_n + 8 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
%C Also numbers n such that (55*10^n+71)/9 is prime.
%C a(10) > 10^5. - _Robert Price_, Sep 08 2015
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/6/61119.htm#prime">Prime numbers of the form 611...119</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A101521(n) + 1.
%t Do[ If[ PrimeQ[(55*10^n + 71)/9], Print[n]], {n, 0, 10000}]
%Y Cf. A002275, A101521.
%K more,nonn
%O 1,1
%A _Robert G. Wilson v_, Jan 18 2005
%E Addition of a(8)-a(9) from Kamada data by _Robert Price_, Dec 13 2010