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 A033003 #10 Feb 05 2014 03:48:44
%S A033003 6,12,18,24,150,162,168,174,300,306,318,324,450,456,462,474,600,606,
%T A033003 612,618,3756,3762,3768,3774,4050,4056,4068,4074,4200,4206,4212,4224,
%U A033003 4350,4356,4362,4368,7506,7512,7518,7524,7650,7662
%N A033003 Every run of digits of n in base 5 has length 2.
%C A033003 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 A033003 Vincenzo Librandi, <a href="/A033003/b033003.txt">Table of n, a(n) for n = 1..1000</a>
%F A033003 a(n) = 6*A043309(n) (= 6*n for n<5). - _M. F. Hasler_, Feb 02 2014
%t A033003 Select[Range[10000],Union[Length/@Split[IntegerDigits[#, 5]]]=={2}&] (* _Vincenzo Librandi_, Feb 05 2014 *)
%K A033003 nonn,base
%O A033003 1,1
%A A033003 _Clark Kimberling_