Now showing items 33-40 of 40

• #### On avoidability of formulas with reversal ﻿

(EDP Sciences, 2018-02-13)
While a characterization of unavoidable formulas (without reversal) is well-known, little is known about the avoidability of formulas with reversal in general. In this article, we characterize the unavoidable formulas ...
• #### Square-free Words with Square-free Self-shuffles ﻿

(The Electronic Journal of Combinatorics, 2014-01-12)
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.
• #### Suffix conjugates for a class of morphic subshifts ﻿

(Cambridge University Press, 2015-09)
Let A be a finite alphabet and f: A^* --> A^* be a morphism with an iterative fixed point f^\omega(\alpha), where \alpha{} is in A. Consider the subshift (X, T), where X is the shift orbit closure of f^\omega(\alpha) and ...
• #### A Ternary Square-free Sequence Avoiding Factors Equivalent to abcacba ﻿

(The Electronic Journal of Combinatorics, 2016-05-27)
We solve a problem of Petrova, finalizing the classification of letter patterns avoidable by ternary square-free words; we show that there is a ternary square-free word avoiding letter pattern xyzxzyx. In fact, we characterize ...
• #### There are Ternary Circular Square-Free Words of Length n for n ≥ 18 ﻿

(The Electronic Journal of Combinatorics, 2002-10-11)
There are circular square-free words of length n on three symbols for n≥18. This proves a conjecture of R. J. Simpson.
• #### There Exist Binary Circular 5/2+ Power Free Words of Every Length ﻿

(The Electronic Journal of Combinatorics, 2004-01-23)
We show that there exist binary circular 5/2+ power free words of every length.
• #### Unary patterns under permutations ﻿

(Elsevier, 2018-06-04)
Thue characterized completely the avoidability of unary patterns. Adding function variables gives a general setting capturing avoidance of powers, avoidance of patterns with palindromes, avoidance of powers under coding, ...