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 A089345 #9 Aug 03 2014 14:26:14
%S A089345 41,61,661,881,2221,4441,6661,6666666661,44444444441,
%T A089345 222222222222222221,666666666666666661,8888888888888888881,
%U A089345 666666666666666666661,6666666666666666666661,4444444444444444444444444441
%N A089345 Primes of the form identical even digits followed by a 1.
%H A089345 Vincenzo Librandi, <a href="/A089345/b089345.txt">Table of n, a(n) for n = 1..37</a>
%t A089345 Select[FromDigits/@Flatten[Table[Join[PadLeft[{n},i,n],{1}],{i,100},{n,2,9,2}],1],PrimeQ] (* _Vincenzo Librandi_, Dec 12 2011 *)
%Y A089345 Cf. A089346, A089347.
%K A089345 base,nonn
%O A089345 1,1
%A A089345 _Amarnath Murthy_, Nov 05 2003
%E A089345 More terms from _Ray Chandler_, Nov 07 2003