The Frobenius problem for the shuffle operation
We characterize the finite sets S of words such that that the iterated shuffle of S is co-finite and we give some bounds on the length of a longest word not in the iterated shuffle of S.
cs.FL↗
arXiv subjects
Jeremy Nicholson
Publications and source records attributed to Jeremy Nicholson.
Initial non-repetitive complexity of infinite words
The initial non-repetitive complexity function of an infinite word x (first defined by Moothathu) is the function of n that counts the number of distinct factors of length n that appear at the beginning of x prior to the first repetition of a length-n factor. We examine general properties of the initial non-repetitive complexity function, as well as obtain formulas for the initial non-repetitive complexity of the Thue-Morse word, the Fibonacci word and the Tribonacci word.
math.CO↗
Improved estimates for the number of privileged words
In combinatorics on words, a word w of length n over an alphabet of size q is said to be privileged if n <= 1 or if n >= 2 and w has a privileged border that occurs exactly twice in w. Forsyth, Jayakumar and Shallit proved that there exist at least 2^{n-5}/n^2 privileged binary words of length n. Using the work of Guibas and Odlyzko, we prove that there are constants c and n_0 such that for n >= n_0, there are at least (cq^n)/(n(\log_q n)^2) privileged words of length n over an alphabet of size q. Thus, for n sufficiently large, we improve the earlier bound set by Forsyth, Jayakumar and Shallit and generalize for all q.
math.CO↗