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%I #20 Jan 17 2019 13:44:07
%S 0,3,4,6,10,12,18,40,48,96,106,114,144,364,618,1090,11370,59454,196684
%N Numbers n such that 4*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 (44*10^n+1)/9 is prime.
%C a(20) > 2*10^5. - _Robert Price_, Mar 30 2015
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/4/48889.htm#prime">Prime numbers of the form 488...889</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A101737(n-1) + 1.
%t Do[ If[ PrimeQ[(44*10^n + 1)/9], Print[n]], {n, 0, 10000}]
%Y Cf. A002275, A101737.
%K more,nonn
%O 1,2
%A _Robert G. Wilson v_, Jan 17 2005
%E Addition of a(16)-a(18) from Kamada data by _Robert Price_, Dec 10 2010
%E 0 added by _Arkadiusz Wesolowski_, Mar 10 2011