A108121 - OEIS

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A108121

A three-symbol substitution sequence with characteristic polynomial: x^3-x^2-2*x-1.

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, 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, 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

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OFFSET

0,1

COMMENTS

This substitution is unique in that it gives a two part tile that only tiles aperiodically.

LINKS

Table of n, a(n) for n=0..104.

FORMULA

1->{2}, 2->{3}, 3->{1, 2, 2, 3}

MATHEMATICA

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]

CROSSREFS