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 A269351 #14 Mar 04 2016 02:30:13
%S A269351 1,9,9,9,9,9,9,9,9,9,1,1,1,1,1,1,1,1,1,9,9,9,9,9,9,9,9,9,1,1,1,1,1,1,
%T A269351 1,1,1,9,9,9,9,9,9,9,9,9,1,1,1,1,1,1,1,1,1,9,9,9,9,9,9,9,9,9,1,1,1,1,
%U A269351 1,1,1,1,1,9,9,9,9,9,9,9,9,9,1,9,1,9
%N A269351 Kolakoski-(1,9) sequence: a(n) is length of n-th run.
%C A269351 19, 199, 1999, 199999, 19999999, 1999999999111111111999999999111111111999999999 are primes.
%H A269351 Vincenzo Librandi, <a href="/A269351/b269351.txt">Table of n, a(n) for n = 1..10000</a>
%H A269351 Michael Baake and Bernd Sing, <a href="http://arXiv.org/abs/math.MG/0206098">Kolakoski-(3,1) is a (deformed) model set</a>, arXiv:math/0206098 [math.MG], 2002-2003.
%t A269351 seed = {1, 9}; w = {}; i = 1; Do[w = Join[w, Array[seed[[Mod[i - 1, Length[seed]] + 1]]&, If[i > Length[w], seed, w][[i]]]]; i++, {n, 42}]; w
%Y A269351 Cf. similar sequences listed in A269268.
%K A269351 nonn,easy
%O A269351 1,2
%A A269351 _Vincenzo Librandi_, Mar 02 2016