A049705 a(n)=3-k(n), where k=A000002=Kolakoski sequence; also the sequence of runlengths of a is k.

2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 2, 1, 1, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Comments

The anti-Kolakoski sequence: a(n) never equals the length of the n-th run. Start with a(1)=2, then the first run is of length 1 and a(2)=1; thus the 2nd run is of length 2 and a(3)=1, thus a(4)=a(5)=2, etc. - Jean-Christophe Hervé, Nov 10 2014

Crossrefs

Cf. A088569 (essentially the same sequence).

Programs

Mathematica

a2 = {1, 2, 2}; Do[ a2 = Join[a2, {1 + Mod[n-1, 2]}], {n, 3, 70}, {i, 1, a2[[n]]}]; 3 - a2 (* Jean-François Alcover, Jun 18 2013 *)