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A219762 Start with 0; repeatedly apply the map {0->012, 1->120, 2->201} to the odd-numbered terms and {0->210, 1->021, 2->102} to the even-numbered terms. 3
0, 1, 2, 0, 2, 1, 2, 0, 1, 2, 1, 0, 2, 0, 1, 0, 2, 1, 2, 0, 1, 2, 1, 0, 1, 2, 0, 1, 0, 2, 1, 2, 0, 2, 1, 0, 2, 0, 1, 2, 1, 0, 1, 2, 0, 2, 1, 0, 2, 0, 1, 0, 2, 1, 2, 0, 1, 2, 1, 0, 1, 2, 0, 1, 0, 2, 1, 2, 0, 2, 1, 0, 1, 2, 0, 1, 0, 2, 0, 1, 2, 0, 2, 1, 0, 1, 2, 1, 0, 2, 1, 2, 0, 1, 0, 2, 0, 1, 2, 1, 0, 2, 1, 2, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

An infinite squarefree sequence over {0,1,2} that is not generated by a CDOL system.

REFERENCES

A. Salomaa, Jewels of Formal Language Theory. Computer Science Press, Rockville, MD, 1981, p. 16, Problem 13.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A099054(n-1) - 1. - Reinhard Zumkeller, Aug 08 2014

EXAMPLE

0 -> 012 -> 012021201 -> ...

MATHEMATICA

f[lst_] := Replace[MapIndexed[{#1, #2[[1]]}&, lst], {{0, n_} :> If[OddQ[n], {0, 1, 2}, {2, 1, 0}], {1, n_} :> If[OddQ[n], {1, 2, 0}, {0, 2, 1}], {2, n_} :> If[OddQ[n], {2, 0, 1}, {1, 0, 2}]}, 1] // Flatten; Nest[f, {0}, 5] (* Jean-Fran├žois Alcover, Mar 07 2014 *)

PROG

(Haskell)

a219762 = subtract 1 . a099054 . subtract 1

-- Reinhard Zumkeller, Aug 08 2014

CROSSREFS

Sequence in context: A127543 A280830 A068907 * A227696 A033687 A263452

Adjacent sequences:  A219759 A219760 A219761 * A219763 A219764 A219765

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 05 2012

STATUS

approved

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Last modified July 8 01:48 EDT 2020. Contains 335502 sequences. (Running on oeis4.)