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 A093404 #22 Jul 08 2021 06:24:16
%S A093404 79,
%T A093404 777777777777777777777777777777777777777777777777777777777777777779,
%U A093404 77777777777777777777777777777777777777777777777777777777777777777777777777777777777779,777777777777777777777777777777777777777777777777777777777777777777777777777777777777777779
%N A093404 Primes of the form 70*R_k + 9, where R_k is the repunit (A002275) of length k.
%C A093404 Primes of the form (7*10^k + 11)/9. - _Vincenzo Librandi_, Nov 16 2010
%H A093404 Makoto Kamada, <a href="https://stdkmd.net/nrr/7/77779.htm#prime">Prime numbers of the form 77...779</a>.
%H A093404 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>
%t A093404 Select[Table[FromDigits[PadLeft[{9},n,7]],{n,100}],PrimeQ] (* _Harvey P. Dale_, May 09 2012 *)
%Y A093404 Cf. A002275, A056693 (corresponding k), A098089.
%K A093404 nonn
%O A093404 1,1
%A A093404 _Rick L. Shepherd_, Mar 28 2004