Lambda Words: A Class of Rich Words Defined Over an Infinite Alphabet
Norman Carey
CUNY Graduate Center
365 Fifth Avenue
New York, NY 10016
USA
Abstract:
Lambda words are sequences obtained by encoding the differences between
ordered elements of the form i + jθ, where i and
j are
non-negative integers and 1 < θ < 2. Lambda words are
right-infinite words defined over an infinite alphabet that have
connections with Sturmian words, Christoffel words, and interspersion
arrays. We show that Lambda words are infinite rich words. Furthermore,
any Lambda word may be mapped onto a right-infinite word over a
three-letter alphabet. Although the mapping preserves palindromes and
non-palindromes of the Lambda word, the resulting Gamma word is not
rich.
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(Concerned with sequences
A022330
A022331
A167267
A216448
A216763
A216764.)
Received September 15 2012;
revised version received January 18 2013; February 17 2013.
Published in Journal of Integer Sequences, March 2 2013.
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