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%I #21 Jan 17 2019 13:44:07
%S 0,1,6,10176,56898
%N Numbers n such that 3*10^n + 8*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
%C Also numbers n such that (35*10^n-17)/9 is prime.
%C a(6) > 10^5. - _Robert Price_, Mar 30 2015
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/3/38887.htm#prime">Prime numbers of the form 388...887</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A101846(n-1) + 1.
%t Do[ If[ PrimeQ[(35*10^n - 17)/9], Print[n]], {n, 0, 10000}]
%Y Cf. A002275, A101846.
%K more,nonn
%O 1,3
%A _Robert G. Wilson v_, Dec 17 2004
%E Additional term 10176 (a PRP) from _Serge Batalov_, Oct 12 2008
%E Addition of a(5) from Kamada data by _Robert Price_, Dec 13 2010
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