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Summary: Hankel determinants of the ThueMorse sequence
J.P. Allouche \Lambda J. Peyri`ere y Z.X. Wen z Z.Y. Wen x
November 5, 1996
Abstract
Let ffl = (ffl n ) n–0 be the ThueMorse sequence, i.e., the sequence defined by the
recurrence equations:
ffl 0 = 1; ffl 2n = ffl n ; ffl 2n+1 = 1 \Gamma ffl n :
We consider fjE p
n jg n–1;p–0 , the double sequence of Hankel determinants (modulo 2)
associated with the ThueMorse sequence. Together with three other sequences, it
obeys a set of sixteen recurrence equations. It shown to be automatic. Applications
are given, namely to combinatorial properties of the ThueMorse sequence and to the
existence of certain Pad'e approximants of the power series
X
n–0
(\Gamma1) ffl n x
n .
0 Introduction
Let S = fa; bg be a twoletter alphabet and S \Lambda the free monoid generated by S. Consider
the endomorphism ` defined on S \Lambda by
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