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A093631 Primes of the form 6*10^k + R_k, where R_k is the repunit (A002275) of length k. 1

%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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Last modified March 28 10:31 EDT 2024. Contains 371240 sequences. (Running on oeis4.)