%I
%S 2,3,3,1,2,3,2,3,3,1,2,3,3,3,1,2,3,1,2,3,2,3,3,1,2,3,3,3,1,2,3,1,2,3,
%T 2,3,3,1,2,3,1,2,3,1,2,3,2,3,3,1,2,3,2,3,3,1,2,3,3,3,1,2,3,1,2,3,2,3,
%U 3,1,2,3,2,3,3,1,2,3,2,3,3,1,2,3,3,3,1,2,3,1,2,3,2,3,3,1,2,3,3,3,1,2,3,1,2
%N Threesymbol substitution based on Rauzy: adding one 3 to second substitution: characteristic polynomial: x^3x^22*x2.
%H Curtis McMullen, <a href="http://projecteuclid.org/euclid.dmj/1150201202">Prym varieties and Teichmüller curves</a>, Duke Math. J., Volume 133, Number 3 (2006), 405616
%F 1>{2}, 2>{3, 3} 3>{1, 2, 3}.
%t s[1] = {2}; s[2] = {3, 3}; s[3] = {1, 2, 3}; t[a_] := Flatten[s /@ a]; p[0] = {1}; p[1] = t[p[0]]; p[n_] := t[p[n  1]] aa = p[7]
%o (PARI) {a(n)=local(A); if(n<1,0, A=[2]; while(length(A)<nA[1]!=2, A=concat(vector(length(A),k,[[2],[3,3],[1,2,3]][A[k]]))); A[n])} /* _Michael Somos_, May 16 2005 */
%K nonn,uned
%O 0,1
%A _Roger L. Bagula_, May 10 2005
