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Form triangle as follows: start with three single digits: 0, 1, 2. Each succeeding row is a concatenation of the previous three rows.
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%I #31 Oct 11 2022 19:35:45

%S 0,1,2,0,1,2,1,2,0,1,2,2,0,1,2,1,2,0,1,2,0,1,2,1,2,0,1,2,2,0,1,2,1,2,

%T 0,1,2,1,2,0,1,2,2,0,1,2,1,2,0,1,2,0,1,2,1,2,0,1,2,2,0,1,2,1,2,0,1,2,

%U 2,0,1,2,1,2,0,1,2,0,1,2,1,2,0,1,2,2,0,1,2,1,2,0,1,2,1,2,0,1,2,2,0,1,2,1,2

%N Form triangle as follows: start with three single digits: 0, 1, 2. Each succeeding row is a concatenation of the previous three rows.

%C Trajectory of 0 under the morphism 0 -> 1, 1-> 2, 2 -> 012. - _Robert G. Wilson v_, May 20 2014

%C The sequence of row lengths is A000213. - _Michael Somos_, May 22 2014

%D C. Pickover, Wonders of Numbers, Oxford University Press, NY, 2001, p. 273.

%H C. A. Pickover, "Wonders of Numbers, Adventures in Mathematics, Mind and Meaning," <a href="http://www.zentralblatt-math.org/zmath/en/search/?q=an:0983.00008&amp;format=complete">Zentralblatt review</a>

%H <a href="/index/Fi#FIXEDPOINTS">Index entries for sequences that are fixed points of mappings</a>

%F a(n) = A059832(n) - 1. - _Sean A. Irvine_, Oct 11 2022

%e Triangle begins:

%e 0

%e 1

%e 2

%e 0 1 2

%e 1 2 0 1 2

%e 2 0 1 2 1 2 0 1 2

%e ...

%p T:= proc(n) option remember;

%p `if`(n<3, n, seq(T(i), i=n-3..n-1))

%p end:

%p seq(T(n), n=0..10); # _Alois P. Heinz_, May 22 2014

%t NestList[ Flatten[# /. {0 -> {1}, 1 -> {2}, 2 -> {0, 1, 2}}] &, {0}, 8] // Flatten (* _Robert G. Wilson v_, May 20 2014 *)

%Y Cf. A059832.

%K easy,nonn,tabf,base

%O 0,3

%A _Jason Earls_, Feb 25 2001

%E More terms from Larry Reeves (larryr(AT)acm.org), Feb 26 2001