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%I #18 Jan 17 2019 13:44:07
%S 0,1,2,7,14,25,116,427,595,637,776,1706,16628,55558
%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-17)/9 is prime.
%C a(15) > 10^5. - _Robert Price_, Jun 05 2015
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/4/48887.htm#prime">Prime numbers of the form 488...887</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A101736(n) + 1.
%t Do[ If[ PrimeQ[(44*10^n - 17)/9], Print[n]], {n, 0, 10000}]
%Y Cf. A002275, A101736.
%K more,nonn
%O 1,3
%A _Robert G. Wilson v_, Jan 17 2005
%E Addition of a(13) from Kamada data by _Robert Price_, Dec 13 2010
%E a(14) from _Robert Price_, Jun 05 2015
%E Prepended a(1) = 0 by _Robert Price_, Jun 05 2015
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