Square-free words obtained from prefixes by permutations
نویسندگان
چکیده
منابع مشابه
On Square-Free Permutations
A permutation is square-free if it does not contain two consecutive factors of length more than one that coincide in the reduced form (as patterns). We prove that the number of square-free permutations of length n is nn(1−εn) where εn → 0 when n → ∞. A permutation of length n is crucial with respect to squares if it avoids squares but any extension of it to the right, to a permutation of length...
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We answer a question of Harju: An infinite square-free ternary word with an n-stem factorization exists for any n ≥ 13. We show that there are uniform ternary morphisms of length k for every k ≥ 23. This resolves almost completely a problem of the author and Rampersad.
متن کاملSquare-free partial words
We say that a partial word w over an alphabet A is square-free if every factor xx of w such that x and x are compatible is either of the form ⋄a or a⋄ where ⋄ is a hole and a ∈ A. We prove that there exist uncountably many square-free partial words over a ternary alphabet with an infinite number of holes.
متن کاملRich square-free words
A word w is rich if it has |w| + 1 many distinct palindromic factors, including the empty word. A word is square-free if it does not have a factor uu, where u is a non-empty word. Pelantová and Starosta (Discrete Math. 313 (2013)) proved that every infinite rich word contains a square. We will give another proof for that result. Pelantová and Starosta denoted by r(n) the length of a longest ric...
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We answer a question of Harju: For every n > 3 there is a square-free ternary word of length n with a square-free self-shuffle.
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ژورنال
عنوان ژورنال: Theoretical Computer Science
سال: 2012
ISSN: 0304-3975
DOI: 10.1016/j.tcs.2011.12.031