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 A093176 #22 Jul 01 2022 18:03:34
%S A093176 71,7777777777771,77777777777777777771,77777777777777777777771,
%T A093176 7777777777777777777777777777771,
%U A093176 7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777771
%N A093176 Primes of the form 70*R_k + 1, where R_k is the repunit (A002275) of length k.
%C A093176 Primes of the form (7*10^k - 61)/9. - _Vincenzo Librandi_, Nov 16 2010
%C A093176 The next term (a(7)) has 241 digits. - _Harvey P. Dale_, Jul 01 2022
%H A093176 Makoto Kamada, <a href="https://stdkmd.net/nrr/7/77771.htm#prime">Prime numbers of the form 77...771</a>.
%H A093176 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>
%F A093176 a(n) = (70*10^A056688(n) - 61)/9 = (7*10^A099419(n) - 61)/9.
%t A093176 Select[Table[FromDigits[PadLeft[{1},n,7]],{n,100}],PrimeQ] (* _Harvey P. Dale_, Jul 01 2022 *)
%Y A093176 Cf. A002275, A056688 (corresponding k), A099419.
%K A093176 nonn
%O A093176 1,1
%A A093176 _Rick L. Shepherd_, Mar 27 2004
%E A093176 Edited by _Ray Chandler_, Mar 06 2012