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Silver dragon four-symbol substitution: characteristic polynomial:x^4-2x^3+x^2-4.
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%I #5 Mar 30 2012 17:34:15

%S 4,3,4,3,2,1,2,3,4,3,4,3,2,1,2,3,2,1,2,1,4,3,4,1,2,1,2,3,2,1,2,3,4,3,

%T 4,3,2,1,2,3,4,3,4,3,2,1,2,3,2,1,2,1,4,3,4,1,2,1,2,3,2,1,2,3,2,1,2,1,

%U 4,3,4,1,2,1,2,1,4,3,4,1,4,3,4,3,2,1,2,3,4,3,4,1,4,3,4,1,2,1,2,1,4,3,4,1,2

%N Silver dragon four-symbol substitution: characteristic polynomial:x^4-2x^3+x^2-4.

%C Entirely new dragon that tiles with self-similar voids: Level 16 to see it: bb = aa /. 1 -> {1, 0} /. 2 -> {0, 1} /. 3 -> {-1, 0} /. 4 -> {0, -1}; ListPlot[FoldList[Plus, {0, 0}, bb], PlotRange -> All, PlotJoined -> True, Axes -> False];

%F 1->{2, 1, 2}, 2->{3}, 3->{4, 3, 4}, 4->{1}

%t s[1] = {2, 1, 2}; s[2] = {3}; s[3] = {4, 3, 4}; s[4] = {1}; t[a_] := Flatten[s /@ a]; p[0] = {1}; p[1] = t[p[0]]; p[n_] := t[p[n - 1]] aa = p[7]

%K nonn,uned

%O 0,1

%A _Roger L. Bagula_, May 06 2005