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%I #24 Jan 17 2019 13:44:07
%S 2,3,6,11,15,26,28,51,150,182,228,407,638,3581,4125,4983,5666,15890,
%T 27743,43362,55367,60744,73701
%N Numbers n such that 4*10^n + 3*R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
%C Also numbers n such that (13*10^n+17)/3 is prime.
%C a(24) > 10^5. - _Robert Price_, Jun 25 2015
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/4/43339.htm#prime">Prime numbers of the form 433...339</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A101725(n) + 1.
%t Do[ If[ PrimeQ[(13*10^n + 17)/3], Print[n]], {n, 0, 10000}]
%Y Cf. A002275, A101725.
%K more,nonn
%O 1,1
%A _Robert G. Wilson v_, Jan 17 2005
%E Addition of a(18)-a(19) from Kamada data by _Robert Price_, Dec 10 2010
%E a(20) from Erik Branger, May 01 2013, submitted by _Ray Chandler_, Aug 16 2013
%E a(21)-a(23) from _Robert Price_, Jun 25 2015
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