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%I #68 May 26 2020 06:27:34
%S 1,3,7,23,59
%N Length of shortest ternary squarefree word having n periods.
%C A word is squarefree if it has no contiguous block inside it of the form xx, for a word x.
%C A period of a word w is an integer 1 <= p <= |w| such that w[i]=w[i+p] for all indices i that make sense. For example, "alfalfa" has period 3. Every nonempty word trivially has a period equal to its length.
%H Daniel Gabric, Narad Rampersad, and Jeffrey Shallit, <a href="https://arxiv.org/abs/2005.11718">An inequality for the number of periods in a word</a>, arXiv:2005.11718 [cs.DM], 2020.
%e Here is a brief table of the lexicographically least words of each length:
%e n=1: 0
%e n=2: 010
%e n=3: 0102010
%e n=4: 01021201021012010212010
%e n=5: 01021201020121020102120102012021020102120102012102010212010.
%K nonn,more
%O 1,2
%A _Jeffrey Shallit_, May 11 2020
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