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%I M0934 #28 Feb 18 2021 12:43:53
%S 2,4,3,2,3,1,2,4,3,1,2,3,2,4,3,2,3,1,2,3,2,4,3,1,2,4,3,2,3,1,2,4,3,1,
%T 2,3,2,4,3,1,2,4,3,2,3,1,2,3,2,4,3,2,3,1,2,4,3,1,2,3,2,4,3,2,3,1,2,3,
%U 2,4,3,1,2,4,3,2,3,1,2,3,2,4,3,2,3,1,2,4,3,1,2,3,2,4,3,1,2,4,3,2,3,1,2,4,3,1,2,3,2,4,3,2,3,1,2
%N A squarefree quaternary sequence.
%C This is an automatic sequence, fixed point starting with 2 of the morphism mu: 1->23, 2->24, 3->31, 4->32. The morphism mu is the 2-block morphism of the Thue-Morse morphism. An instance of this sequence on the alphabet {0,1,2,3} is equal to A245188. - _Michel Dekking_, Feb 18 2021
%D A. Salomaa, Jewels of Formal Language Theory. Computer Science Press, Rockville, MD, 1981, p. 10.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H Sean A. Irvine, <a href="/A005681/b005681.txt">Table of n, a(n) for n = 1..10000</a>
%H F. Michel Dekking, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL19/Dekking/dekk4.html">Morphisms, Symbolic Sequences, and Their Standard Forms</a>, Journal of Integer Sequences, Vol. 19 (2016), Article 16.1.1.
%H G. Siebert, <a href="/A001285/a001285_1.pdf">Letter to N. J. A. Sloane, Sept. 1977</a>
%F a(n) = s(A001285(n), A001285(n+1)) where s(1,1)=1, s(1,2)=2, s(2,1)=3, s(2,2)=4. - _Sean A. Irvine_, Aug 04 2016
%Y Cf. A001285, A005679, A245188.
%K nonn
%O 1,1
%A _N. J. A. Sloane_