Displaying similar documents to “How many squares must a binary sequence contain?”

On the number of squares in partial words

Vesa Halava, Tero Harju, Tomi Kärki (2010)

RAIRO - Theoretical Informatics and Applications

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The theorem of Fraenkel and Simpson states that the maximum number of distinct squares that a word  of length  can contain is less than . This is based on the fact that no more than two squares can have their last occurrences starting at the same position. In this paper we show that the maximum number of the last occurrences of squares per position in a partial word containing one hole is , where is the size of the alphabet. Moreover, we prove that the number of distinct squares in...

Infinite words containing squares at every position

James Currie, Narad Rampersad (2010)

RAIRO - Theoretical Informatics and Applications

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Richomme asked the following question: what is the infimum of the real numbers > 2 such that there exists an infinite word that avoids -powers but contains arbitrarily large squares beginning at every position? We resolve this question in the case of a binary alphabet by showing that the answer is = 7/3.

Squares and overlaps in the Thue-Morse sequence and some variants

Shandy Brown, Narad Rampersad, Jeffrey Shallit, Troy Vasiga (2006)

RAIRO - Theoretical Informatics and Applications

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We consider the position and number of occurrences of squares in the Thue-Morse sequence, and show that the corresponding sequences are -regular. We also prove that changing any finite but nonzero number of bits in the Thue-Morse sequence creates an overlap, and any linear subsequence of the Thue-Morse sequence (except those corresponding to decimation by a power of ) contains an overlap.

A note on the number of squares in a partial word with one hole

Francine Blanchet-Sadri, Robert Mercaş (2009)

RAIRO - Theoretical Informatics and Applications

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A well known result of Fraenkel and Simpson states that the number of distinct squares in a word of length is bounded by since at each position there are at most two distinct squares whose last occurrence starts. In this paper, we investigate squares in partial words with one hole, or sequences over a finite alphabet that have a “do not know” symbol or “hole”. A square in a partial word over a given alphabet has the form where is with , and consequently, such square is compatible...