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 A090154 #5 Mar 30 2012 17:30:56
%S A090154 61,67,677,67777,611111,61111111,67777777777,67777777777777,
%T A090154 61111111111111111111111111,67777777777777777777777777,
%U A090154 61111111111111111111111111111111
%N A090154 Primes of the form identical digits preceded by a 6.
%H A090154 Vincenzo Librandi, <a href="/A090154/b090154.txt">Table of n, a(n) for n = 1..23</a>
%t A090154 Select[ FromDigits /@ Flatten[ Table[ PadRight[{6}, i, # ] & /@ {1, 2, 3, 4, 5, 6, 7, 8, 9}, {i, 2, 100}], 1], PrimeQ[ # ] &]
%K A090154 nonn,base
%O A090154 1,1
%A A090154 _Robert G. Wilson v_, Nov 22 2003