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 A089347 #11 Mar 29 2015 12:11:59
%S A089347 11,31,41,61,71,331,661,881,991,2221,3331,4441,6661,33331,99991,
%T A089347 333331,3333331,9999991,33333331,6666666661,44444444441,555555555551,
%U A089347 5555555555551,7777777777771,222222222222222221,333333333333333331
%N A089347 Primes of the form identical digits followed by a 1.
%H A089347 Vincenzo Librandi, <a href="/A089347/b089347.txt">Table of n, a(n) for n = 1..80</a>
%t A089347 Select[ FromDigits /@ Flatten[ Table[ PadLeft[{1}, i, # ] & /@ {1, 2, 3, 4, 5, 6, 7, 8, 9}, {i, 2, 18}], 1], PrimeQ[ # ] &] (* _Robert G. Wilson v_, Nov 15 2003 *)
%Y A089347 Cf. A089345, A089346.
%K A089347 base,nonn
%O A089347 1,1
%A A089347 _Amarnath Murthy_, Nov 05 2003
%E A089347 More terms from _Ray Chandler_ and _Robert G. Wilson v_, Nov 07 2003