A122497 Let f(S) denote the interchange of 1's and 2's in S. Let S_0 = 1, S_{N+1} = f(S_N).S_N, where the dot indicates concatenation. Sequence gives S_0.S_1.S_2.S_3....

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

Offset

1,2

Comments

An alternating triangular Morse-Thue sequence based on A010060 using {1,2} instead of {0,1} substitutions.

Links

G. C. Greubel, Table of n, a(n) for the first 13 rows, flattened

Eric Weisstein's World of Mathematics, Thue-Morse Constant

Formula

a(n) = A059448(n) + 1. - Filip Zaludek, Dec 10 2016

Example

The first few S_i are:
1
2, 1
1, 2, 2, 1
2, 1, 1, 2, 1, 2, 2, 1
1, 2, 2, 1, 2, 1, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1

Mathematica

ThueMorse[n_, b_] := Nest[Flatten[ # /. {1 -> {1, 2}, 2 -> {2, 1}}] &, {b}, n] a = Table[ThueMorse[n, 1 + Mod[n, 2]], {n, 0, 7}] Flatten[a]

Crossrefs

Cf. A010060, A014571, A014572, A074072, A074073.

Sequence in context: A049705 A060236 A006345 * A350330 A154402 A210682

Adjacent sequences: A122494 A122495 A122496 * A122498 A122499 A122500

Keyword

nonn,tabf

Author

Roger L. Bagula, Sep 15 2006

Extensions

Edited by N. J. A. Sloane, May 22 2007

Status

approved