This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A093166 #21 Jul 08 2021 05:53:25
%S A093166 3,83,883,88883,88888883,888888883,888888888888883,
%T A093166 888888888888888888888888888888888888888888888888883,
%U A093166 88888888888888888888888888888888888888888888888888888888888888888888883
%N A093166 Primes of the form 80*R_k + 3, where R_k is the repunit (A002275) of length k.
%C A093166 Primes of the form (8*10^k - 53)/9. - _Vincenzo Librandi_, Nov 16 2010
%H A093166 Makoto Kamada, <a href="https://stdkmd.net/nrr/8/88883.htm#prime">Prime numbers of the form 88...883</a>.
%H A093166 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>
%t A093166 Select[Table[FromDigits[PadLeft[{3},n,8]],{n,80}],PrimeQ] (* _Harvey P. Dale_, Sep 21 2013 *)
%Y A093166 Cf. A002275, A056694 (corresponding k), A099422.
%K A093166 nonn
%O A093166 1,1
%A A093166 _Rick L. Shepherd_, Mar 26 2004