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 A033007 #10 Feb 05 2014 03:48:49
%S A033007 10,20,30,40,50,60,70,80,810,830,840,850,860,870,880,890,1620,1630,
%T A033007 1650,1660,1670,1680,1690,1700,2430,2440,2450,2470,2480,2490,2500,
%U A033007 2510,3240,3250,3260,3270,3290,3300,3310,3320,4050
%N A033007 Every run of digits of n in base 9 has length 2.
%C A033007 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 A033007 Vincenzo Librandi, <a href="/A033007/b033007.txt">Table of n, a(n) for n = 1..1000</a>
%F A033007 a(n) = 10*A043313(n) (= 10*n for n<9). - _M. F. Hasler_, Feb 02 2014
%t A033007 Select[Range[10000], Union[Length/@Split[IntegerDigits[#, 9]]]=={2}&] (* _Vincenzo Librandi_, Feb 05 2014 *)
%K A033007 nonn,base
%O A033007 1,1
%A A033007 _Clark Kimberling_