A071820 Kolakoski-(2,3) sequence: a(n) is length of n-th run.

2, 2, 3, 3, 2, 2, 2, 3, 3, 3, 2, 2, 3, 3, 2, 2, 3, 3, 3, 2, 2, 2, 3, 3, 3, 2, 2, 3, 3, 2, 2, 2, 3, 3, 3, 2, 2, 3, 3, 2, 2, 2, 3, 3, 3, 2, 2, 2, 3, 3, 2, 2, 3, 3, 2, 2, 2, 3, 3, 3, 2, 2, 2, 3, 3, 2, 2, 3, 3, 3, 2, 2, 2, 3, 3, 2, 2, 3, 3, 2, 2, 2, 3, 3, 3, 2, 2, 2, 3, 3, 2, 2, 3, 3, 3, 2, 2, 2, 3, 3, 2, 2, 3, 3, 2

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Links

• Ivan Neretin, Table of n, a(n) for n = 1..10000
• Michael Baake and Bernd Sing, Kolakoski-(3,1) is a (deformed) model set, arXiv:math/0206098 [math.MG], 2002-2003.
• Johan Nilsson, A Space-Efficient Algorithm for Calculating the Digit Distribution in the Kolakoski Sequence, J. Int. Seq. 15 (2012) #12.6.7.
• Ulrich Reitebuch, Henriette-Sophie Lipschütz, and Konrad Polthier, Visualizing the Kolakoski Sequence, Bridges Conf. Proc.; Math., Art, Music, Architecture, Culture (2023) 481-484.

Crossrefs

Cf. A000002, A064353, A071907, A071928, A071942.

Programs

Mathematica

seed = {2, 3};
w = {};
i = 1;
Do[
  w = Join[w,
    Array[seed[[Mod[i - 1, Length[seed]] + 1]] &,
     If[i > Length[w], seed, w][[i]]]];
  i++
  , {n, 43}];
w
(* Ivan Neretin, Apr 01 2015 *)

Extensions

More terms from Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), Sep 08 2002