No extremal square-free words over large alphabets
Published Web Locationhttps://doi.org/10.5070/C62156889
A word is square-free if it does not contain any square (a word of the form $XX$), and is extremal square-free if it cannot be extended to a new square-free word by inserting a single letter at any position. Grytczuk, Kordulewski, and Niewiadomski proved that there exist infinitely many ternary extremal square-free words. We establish that there are no extremal square-free words over any alphabet of size at least $17$.
Mathematics Subject Classifications: 05A05, 05D10, 68R15