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%I #19 Jul 08 2021 05:54:13
%S 29,229,22229,22222222222229
%N Primes of the form 20*R_k + 9, where R_k is the repunit (A002275) of length k.
%C a(5) has 176 digits, a(6) has 416 digits. - _Vincenzo Librandi_, Dec 10 2010; _Bruno Berselli_, Jul 17 2012
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/2/22229.htm#prime">Prime numbers of the form 22...229</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>
%Y Cf. A002275, A056678 (corresponding k), A099410.
%K nonn
%O 1,1
%A _Rick L. Shepherd_, Mar 28 2004
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