

A291793


Period of orbit of Post's tag system applied to the word (100)^n (version 2), or 1 if the orbit increases without limit.


6



2, 6, 6, 6, 0, 10, 28, 6, 10, 6, 6, 6, 0, 0, 6, 28, 10, 6, 10, 6, 6, 0, 6, 6, 0, 6, 6, 6, 6, 6, 6, 52, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 28, 6, 0, 0, 28, 6, 6, 6, 6, 6, 0, 6, 6, 6, 10, 6, 6, 6, 6, 0, 6, 0, 6, 6, 6, 6, 0, 6, 6, 6, 0, 6, 6, 6, 0, 10, 0, 10, 6, 6
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OFFSET

1,1


COMMENTS

Post's tag system maps a word w over {0,1} to w', where if w begins with 0, w' is obtained by appending 00 to w and deleting the first three letters, or if w begins with 1, w' is obtained by appending 1101 to w and deleting the first three letters.
The empty word is included in the count.
Here, following Asveld, a(n)=0 if the orbit ends at the empty word. On the other hand, Shallit defines a(n) to be 1 if that happens, which gives a different sequence, A284121.


LINKS

Lars Blomberg, Table of n, a(n) for n = 1..6075
Peter R. J. Asveld, On a Post's System of Tag. Bulletin of the EATCS 36 (1988), 96102.
Lars Blomberg, Histogram over nonzero terms


EXAMPLE

For n = 2 the orbit of (100)^2 = 100100 consists of a preperiod of length 15, followed by a periodic portion of length 6.


CROSSREFS

Cf. A284116, A284119, A291792, A284121.
Sequence in context: A065486 A069806 A123945 * A284121 A198102 A097466
Adjacent sequences: A291790 A291791 A291792 * A291794 A291795 A291796


KEYWORD

nonn


AUTHOR

N. J. A. Sloane, Sep 04 2017, based on Jeffrey Shallit's A284121.


EXTENSIONS

a(50)a(83) from Lars Blomberg, Sep 08 2017


STATUS

approved



