%I #21 Jul 08 2021 05:53:25

%S 3,83,883,88883,88888883,888888883,888888888888883,

%T 888888888888888888888888888888888888888888888888883,

%U 88888888888888888888888888888888888888888888888888888888888888888888883

%N Primes of the form 80*R_k + 3, where R_k is the repunit (A002275) of length k.

%C Primes of the form (8*10^k - 53)/9. - _Vincenzo Librandi_, Nov 16 2010

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/8/88883.htm#prime">Prime numbers of the form 88...883</a>.

%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>

%t Select[Table[FromDigits[PadLeft[{3},n,8]],{n,80}],PrimeQ] (* _Harvey P. Dale_, Sep 21 2013 *)

%Y Cf. A002275, A056694 (corresponding k), A099422.

%K nonn

%O 1,1

%A _Rick L. Shepherd_, Mar 26 2004