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%I #13 Jan 17 2019 13:44:07
%S 2,3,6,17,20,45,57,78,119,137,509,710,1127,1518,1761,3086,3147,9926,
%T 19854,27842,46799,49682,68718,100542,106649,191073
%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+1)/9 is prime.
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/3/38889.htm#prime">Prime numbers of the form 388...889</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A101847(n) + 1.
%t Do[ If[ PrimeQ[(35*10^n + 1)/9], Print[n]], {n, 0, 10000}]
%Y Cf. A002275, A101847.
%K more,nonn
%O 1,1
%A _Robert G. Wilson v_, Dec 21 2004
%E Addition of a(19)-a(26) from Kamada data by _Robert Price_, Dec 08 2010
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