Is there a common name in combinatorics for words that do not have square of size 1 ? That is words such that no symbols appears twice in a row or, more formally, words not in $\bigcup_{s\in\Sigma} \Sigma^* s s \Sigma^*$ where $\Sigma$ is our alphabet.

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    $\begingroup$ I propose calling the occurrence of a repeated letter a “hiccup” and correspondingly calling your language hiccup-free. $\endgroup$
    – Aryeh
    Commented Jan 31, 2022 at 17:38

1 Answer 1


I would call them stutter-free words, since there is the notion of stutter-invariant language, which is already well-known.


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