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%I M0134 #21 Nov 09 2020 00:00:36
%S 1,2,1,3,2,1,2,3,1,2,1,3,2,3,1,3,2,1,2,3,1,2,1,3,2,1,2,3,1,3,2,3,1,2,
%T 1,3,2,1,2,3,1,2,1,3,2,3,1,3,2,1,2,3,1,3,2,3,1,2,1,3,2,3,1,3,2,1,2,3,
%U 1,2,1,3,2,1,2,3,1,3,2,3,1,2,1,3,2,1,2
%N A squarefree ternary sequence.
%C Rules: 1 -> 1213, 2 -> 2123, 3 preceded by 1 -> 2313, 3 preceded by 2 -> 1323. - _Sean A. Irvine_, Nov 08 2020
%D G. Siebert, personal communication.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%D A. Thue. Über unendliche Zeichenreihen, Norske Vid. Selsk. Skr. I. Mat. Nat. Kl. Christiania, No. 7 (1906), 1-22. See p. 14.
%H J. Berstel, <a href="http://www-igm.univ-mlv.fr/~berstel/Articles/1994ThueTranslation.pdf">Axel Thue's papers on repetitions in words: a translation</a>, 1994.
%H G. Siebert, <a href="/A001285/a001285_1.pdf">Letter to N. J. A. Sloane, Sept. 1977</a>
%K nonn
%O 1,2
%A _N. J. A. Sloane_
%E More terms from _Sean A. Irvine_, Nov 08 2020