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 A043638 #17 Apr 25 2021 12:18:52
%S A043638 10,12,13,14,15,16,17,18,19,20,21,23,24,25,26,27,28,29,30,31,32,34,35,
%T A043638 36,37,38,39,40,41,42,43,45,46,47,48,49,50,51,52,53,54,56,57,58,59,60,
%U A043638 61,62,63,64,65,67,68,69,70,71,72,73,74,75,76,78,79,80,81,82,83,84,85,86,87,89,90,91,92,93,94,95,96,97,98,100,110,112,113,114,115,116,117,118,119,122,133,144,155,166,177,188,199,200
%N A043638 Numbers whose base-10 representation has exactly 2 runs.
%C A043638 Coincides with sequence "Number of runs in the base 10 representation of n is even" until reaching 1234.
%C A043638 From _Robert Israel_, Sep 26 2016: (Start)
%C A043638 Numbers of the form (a*(10^i-10^j) + b*(10^j-1))/9 for some i > j >= 0, a <> b with 1 <= a <= 9, 0 <= b <= 9.
%C A043638 There are 81*(d-1) terms with d digits for each d >= 2. (End)
%H A043638 Robert Israel, <a href="/A043638/b043638.txt">Table of n, a(n) for n = 1..10000</a>
%p A043638 sort([seq(seq(seq(seq((a*(10^i-10^j)+b*(10^j-1))/9, a={$1..9} minus {b}),b=0..9),j=1..i-1),i=2..4)]); # _Robert Israel_, Sep 26 2016
%Y A043638 Cf. A023752.
%K A043638 nonn,base,easy
%O A043638 1,1
%A A043638 _Clark Kimberling_