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%I #21 Jul 08 2021 06:20:43
%S 7,887,8887,888887,888888887,888888888887,
%T 888888888888888888888888888888888888888888888888888888888888888888888887
%N Primes of the form 80*R_k + 7, where R_k is the repunit (A002275) of length k.
%C Primes of the form (8*10^k - 17)/9. - _Vincenzo Librandi_, Nov 16 2010
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/8/88887.htm#prime">Prime numbers of the form 88...887</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>
%Y Cf. A056695 (corresponding k), A096846.
%K nonn
%O 1,1
%A _Rick L. Shepherd_, Mar 26 2004
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