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%I #4 Mar 30 2012 17:34:16
%S 3,1,2,2,3,1,2,2,3,2,3,3,1,2,2,3,1,2,2,3,2,3,3,1,2,2,3,2,3,3,1,2,2,3,
%T 3,1,2,2,3,1,2,2,3,2,3,3,1,2,2,3,1,2,2,3,2,3,3,1,2,2,3,2,3,3,1,2,2,3,
%U 3,1,2,2,3,1,2,2,3,2,3,3,1,2,2,3,2,3,3,1,2,2,3,3,1,2,2,3,1,2,2,3,2,3,3,1,2
%N A three-symbol substitution sequence with characteristic polynomial: x^3-x^2-2*x-1.
%C This substitution is unique in that it gives a two part tile that only tiles aperiodically.
%F 1->{2}, 2->{3}, 3->{1, 2, 2, 3}
%t s[1] = {2}; s[2] = {3}; s[3] = {1, 2, 2, 3}; t[a_] := Flatten[s /@ a]; p[0] = {1}; p[1] = t[p[0]]; p[n_] := t[p[n - 1]] aa = p[8]
%K nonn,uned
%O 0,1
%A _Roger L. Bagula_, Jun 04 2005