%I #16 Jul 08 2021 05:59:34
%S 61,611111,61111111,61111111111111111111111111,
%T 61111111111111111111111111111111,
%U 61111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
%N Primes of the form 6*10^k + R_k, where R_k is the repunit (A002275) of length k.
%C The next term has 200 digits. - _Harvey P. Dale_, Dec 06 2019
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/6/61111.htm#prime">Prime numbers of the form 611...11</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>
%t Select[Table[FromDigits[PadRight[{6},n,1]],{n,150}],PrimeQ] (* _Harvey P. Dale_, Dec 06 2019 *)
%Y Cf. A002275, A056717 (corresponding k).
%K nonn
%O 1,1
%A _Rick L. Shepherd_, Apr 06 2004
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