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 A033009 #11 Feb 05 2014 08:09:08
%S A033009 12,24,36,48,60,72,84,96,108,120,1452,1476,1488,1500,1512,1524,1536,
%T A033009 1548,1560,1572,2904,2916,2940,2952,2964,2976,2988,3000,3012,3024,
%U A033009 4356,4368,4380,4404,4416,4428,4440,4452,4464,4476
%N A033009 Every run of digits of n in base 11 has length 2.
%C A033009 See A043291 and A033001 through A033014 for the analog in other bases, A033015 - A033029 for the variants with run lengths >= 2. - _M. F. Hasler_, Feb 02 2014
%H A033009 Vincenzo Librandi, <a href="/A033009/b033009.txt">Table of n, a(n) for n = 1..1100</a>
%F A033009 a(n) = 12*A043315(n) (= 12*n for n<11). - _M. F. Hasler_, Feb 02 2014
%t A033009 Select[Range[10000], Union[Length/@Split[IntegerDigits[#, 11]]]=={2}&] (* _Vincenzo Librandi_, Feb 05 2014 *)
%K A033009 nonn,base
%O A033009 1,1
%A A033009 _Clark Kimberling_