

A005679


A squarefree (or ThueMorse) ternary sequence: closed under a>abc, b>ac, c>b.
(Formerly M0140)


4



2, 1, 3, 2, 3, 1, 2, 1, 3, 1, 2, 3, 2, 1, 3, 2, 3, 1, 2, 3, 2, 1, 3, 1, 2, 1, 3, 2, 3, 1, 2, 1, 3, 1, 2, 3, 2, 1, 3, 1, 2, 1, 3, 2, 3, 1, 2, 3, 2, 1, 3, 2, 3, 1, 2, 1, 3, 1, 2, 3, 2, 1, 3, 2, 3, 1, 2, 3, 2, 1, 3, 1, 2, 1, 3, 2, 3, 1, 2, 3, 2, 1, 3, 2, 3, 1, 2, 1, 3, 1, 2, 3, 2, 1, 3, 1, 2, 1, 3, 2, 3, 1, 2, 1, 3
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OFFSET

1,1


COMMENTS

Trajectory of 2 under the morphism 1 > 23, 2 > 213 & 3 > 1.  Robert G. Wilson v, Apr 06 2008
Replace all 4's in A005681 with 1's and you get this sequence.  Sean A. Irvine, Aug 04 2016


REFERENCES

A. Salomaa, Jewels of Formal Language Theory. Computer Science Press, Rockville, MD, 1981, p. 10.
G. Siebert, personal communication.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

Table of n, a(n) for n=1..105.
Marston Morse and Gustav A. Hedlund, Unending chess, symbolic dynamics and a problem in semigroups, Duke Math. J., Volume 11, Number 1 (1944), 17.
G. Siebert, Letter to N. J. A. Sloane, Sept. 1977
Index entries for sequences that are fixed points of mappings


MATHEMATICA

Nest[ # /. {1 > {2, 3}, 2 > {2, 1, 3}, 3 > 1} &, {2}, 7] // Flatten (* Robert G. Wilson v, Apr 06 2008 *)


CROSSREFS

Cf. A005681.
Sequence in context: A048233 A287730 A260452 * A232927 A275832 A237839
Adjacent sequences: A005676 A005677 A005678 * A005680 A005681 A005682


KEYWORD

nonn,easy,nice


AUTHOR

N. J. A. Sloane


EXTENSIONS

More terms from Robert G. Wilson v, Apr 06 2008


STATUS

approved



