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 A089346 #11 Dec 05 2013 19:56:35
%S A089346 11,31,71,331,991,3331,33331,99991,333331,3333331,9999991,33333331,
%T A089346 555555555551,5555555555551,7777777777771,333333333333333331,
%U A089346 1111111111111111111,77777777777777777771,11111111111111111111111
%N A089346 Primes of the form identical odd digits followed by a 1.
%H A089346 Vincenzo Librandi, <a href="/A089346/b089346.txt">Table of n, a(n) for n = 1..44</a>
%t A089346 Select[FromDigits/@Flatten[Table[Join[PadLeft[{n},i,n],{1}],{i,25},{n,1,9,2}], 1],PrimeQ] (* _Harvey P. Dale_, Jul 25 2011 *)
%Y A089346 Cf. A089345, A089347.
%K A089346 base,nonn
%O A089346 1,1
%A A089346 _Amarnath Murthy_, Nov 05 2003
%E A089346 More terms from _Ray Chandler_, Nov 07 2003