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 A093174 #17 Jul 08 2021 06:23:46 %S A093174 41,4441,44444444441,4444444444444444444444444441, %T A093174 4444444444444444444444444444444444444444444444444444441, %U A093174 4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444441 %N A093174 Primes of the form 40*R_k + 1, where R_k is the repunit (A002275) of length k. %C A093174 Primes of the form (4*10^k - 31)/9. - _Vincenzo Librandi_, Nov 16 2010 %H A093174 Makoto Kamada, <a href="https://stdkmd.net/nrr/4/44441.htm#prime">Prime numbers of the form 44...441</a>. %H A093174 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a> %Y A093174 Cf. A056681 (corresponding k), A173768. %K A093174 nonn %O A093174 1,1 %A A093174 _Rick L. Shepherd_, Mar 27 2004 %E A093174 Edited by _N. J. A. Sloane_, Feb 26 2010