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 A269268 #27 Sep 04 2019 17:23:40
%S A269268 1,5,5,5,5,5,1,1,1,1,1,5,5,5,5,5,1,1,1,1,1,5,5,5,5,5,1,5,1,5,1,5,5,5,
%T A269268 5,5,1,1,1,1,1,5,5,5,5,5,1,1,1,1,1,5,5,5,5,5,1,5,1,5,1,5,5,5,5,5,1,1,
%U A269268 1,1,1,5,5,5,5,5,1,1,1,1,1,5,5,5,5,5,1
%N A269268 Kolakoski-(1,5) sequence: a(n) is length of n-th run.
%C A269268 15555511, 155555111, 155555111115555511111 are primes.
%C A269268 The fraction of 5s in this sequence approaches ((3+2*sqrt(2))^(1/3)+(3-2*sqrt(2))^(1/3))/4 ~ 0.588825 -- see the formula in A064353. - _Ed Wynn_, Sep 04 2019
%H A269268 Vincenzo Librandi, <a href="/A269268/b269268.txt">Table of n, a(n) for n = 1..10000</a>
%H A269268 Michael Baake and Bernd Sing, <a href="https://arxiv.org/abs/math/0206098">Kolakoski-(3,1) is a (deformed) model set</a>, arXiv:math/0206098 [math.MG], 2002-2003.
%t A269268 seed = {1, 5}; w = {}; i = 1; Do[w = Join[w, Array[seed[[Mod[i - 1, Length[seed]] + 1]] &, If[i > Length[w], seed, w][[i]]]]; i++, {n, 250}]; w (* from _Ivan Neretin_ in similar sequences *)
%Y A269268 Cf. Kolakoski-(1,k) sequence: A000002 (k=2), A064353 (k=3), A071907 (k=4), this sequence (k=5), A269348 (k=6), A269349 (k=7), A269350 (k=8), A269351 (k=9), A269352 (k=10).
%K A269268 nonn,easy
%O A269268 1,2
%A A269268 _Vincenzo Librandi_, Feb 25 2016