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 A118270 #17 Feb 16 2025 08:33:01
%S A118270 7,9,4,5,0,7,1,9,2,7,7,9,4,7,9,2,7,6,2,4,0,3,6,2,4,1,5,6,3,6,0,4,5,6,
%T A118270 4,6,2,9,8,5,7,7,1,0,0,9,8,8,6,0,6,9,6,7,2,6,5,8,8,6,7,3,7,1,5,3,8,1,
%U A118270 4,7,7,5,0,2,4,6,0,5,0,1,5,3,6,4,2,3,2,9,4,9,7,3,1,8,7,4,4,9,2,2,5,9,7,6,5
%N A118270 Decimal expansion of Kolakoski constant.
%H A118270 Rabie A. Mahmoud, <a href="http://www.researchgate.net/profile/Rabie_Mahmoud2/publication/271910838">Hardware Implementation of Binary Kolakoski Sequence</a>, Research Gate, 2015.
%H A118270 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/KolakoskiSequence.html">Kolakoski Sequence</a>
%F A118270 Take the Kolakoski sequence (A000002) 1221121221.... Interpret the 2's as 1's and the 1's as 0's: 0110010110.... Interpret the result as a binary fraction: 0.110010110..._2.
%e A118270 0.7945071927794792762...
%t A118270 A000002[n_] := (s = {1, 2, 2}; Do[AppendTo[s, Mod[k-1, 2] + 1], {k, 3, n}, {s[[k]]}] ; s); Take[ First[ RealDigits[ FromDigits[ {Rest[A000002[300] /. {1 -> 0, 2 -> 1}], 0}, 2]]], 105] (* _Jean-François Alcover_, Jul 28 2011 *)
%Y A118270 Cf. A000002.
%K A118270 nonn,cons
%O A118270 0,1
%A A118270 _Eric W. Weisstein_, Apr 21 2006