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 A093169 #16 Jul 08 2021 06:24:32 %S A093169 7,557,5557,555557,5555555557,555555555555557,5555555555555555555557, %T A093169 5555555555555555555555555555555555555555555555555555555555555555555555555555555555555557 %N A093169 Primes of the form 50*R_k + 7, where R_k is the repunit (A002275) of length k. %C A093169 Primes of the form (5*10^k + 13)/9. - _Vincenzo Librandi_, Nov 16 2010 %H A093169 Makoto Kamada, <a href="https://stdkmd.net/nrr/5/55557.htm#prime">Prime numbers of the form 55...557</a>. %H A093169 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a> %Y A093169 Cf. A056686 (corresponding k). %K A093169 nonn %O A093169 1,1 %A A093169 _Rick L. Shepherd_, Mar 26 2004