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%I #14 Oct 02 2016 10:15:05
%S 1,2,2,2,1,4,3,3,3,4,4,3,3,3,4,4,3,3,3,4,1,2,2,2,1,3,4,4,4,3,2,1,1,1,
%T 2,2,1,1,1,2,2,1,1,1,2,3,4,4,4,3,3,4,4,4,3,2,1,1,1,2,2,1,1,1,2,2,1,1,
%U 1,2,3,4,4,4,3,3,4,4,4,3,2,1,1,1,2,2,1,1,1,2,2,1,1,1,2,3,4,4,4,3,1,2,2,2,1
%N Trajectory of 1 under the morphism 1->{1,2,2,2,1}, 2->{4,3,3,3,4}, 3->{2,1,1,1,2}, 4->{3,4,4,4,3}.
%C Edgar-Peano substitution of 4 symbols taken 5 at a time: characteristic polynomial -x^5 + 5*x^3 + 5*x^2 - 25*x.
%H F. M. Dekking, <a href="http://dx.doi.org/10.1016/0001-8708(82)90066-4">Recurrent sets</a>, Advances in Mathematics, 44 (1982), 78-104.
%H G. A. Edgar and Jeffery Golds, <a href="http://arxiv.org/abs/math/9806039">A Fractal Dimension Estimate for a Graph-Directed IFS of Non-Similarities</a>, arXiv:math/9806039 [math.CA], 1991
%H <a href="/index/Fi#FIXEDPOINTS">Index entries for sequences that are fixed points of mappings</a>
%t s[1] = {1, 2, 2, 2, 1}; s[2] = {4, 3, 3, 3, 4}; s[3] = {2, 1, 1, 1, 2}; s[4] = {3, 4, 4, 4, 3}; s[5] = {} t[a_] := Flatten[s /@ a]; p[0] = {1}; p[1] = t[p[0]]; p[n_] := t[p[n - 1]]; aa = p[3]
%o (PARI) {a(n)=local(A); if(n<1,0, A=[1]; while(length(A)<n, A=concat(vector(length(A),k,[1,2,2,2,1;4,3,3,3,4;2,1,1,1,2;3,4,4,4,3][A[k],]))); A[n])} /* _Michael Somos_, May 16 2005 */
%K nonn
%O 0,2
%A _Roger L. Bagula_, May 04 2005
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