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%I #20 Jan 17 2019 13:44:07
%S 1,4,84,165,274,513,3372,4177,4318,10579,17221,19672,20065,36646,
%T 40191,55359,86230
%N Numbers n such that 4*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 (37*10^n+53)/9 is prime.
%C a(18) > 10^5. - _Robert Price_, May 10 2015
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/4/41117.htm#prime">Prime numbers of the form 411...117</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A101717(n) + 1.
%t Do[ If[ PrimeQ[(37*10^n + 53)/9], Print[n]], {n, 0, 10000}]
%Y Cf. A002275, A101717.
%K more,nonn
%O 1,2
%A _Robert G. Wilson v_, Dec 21 2004
%E Addition of a(10)-a(13) from Kamada data by _Robert Price_, Dec 13 2010
%E a(14)-a(15) from Erik Branger May 01 2013 by _Ray Chandler_, Aug 16 2013
%E a(16)-a(17) from _Robert Price_, May 10 2015
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