%I A108121
%S A108121 3,1,2,2,3,1,2,2,3,2,3,3,1,2,2,3,1,2,2,3,2,3,3,1,2,2,3,2,3,3,1,2,2,3,3,
%T A108121 1,2,2,3,1,2,2,3,2,3,3,1,2,2,3,1,2,2,3,2,3,3,1,2,2,3,2,3,3,1,2,2,3,3,1,
%U A108121 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 A108121 A three-symbol substitution sequence with characteristic polynomial: 
               x^3-x^2-2*x-1.
%C A108121 This substitution is unique in that it gives a two part tile that only 
               tiles aperiodically.
%F A108121 1->{2}, 2->{3}, 3->{1, 2, 2, 3}
%t A108121 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]
%Y A108121 Sequence in context: A144148 A085247 A003016 this_sequence A161916 A072548 
               A079399
%Y A108121 Adjacent sequences: A108118 A108119 A108120 this_sequence A108122 A108123 
               A108124
%K A108121 nonn,uned
%O A108121 0,1
%A A108121 Roger L. Bagula (rlbagulatftn(AT)yahoo.com), Jun 04 2005