Existence of a nonrepetitive palindrome-free sequence avoiding two subsequences

From papers

Let an infinite sequence be a sequence whose terms are drawn from the four-letter alphabet {A,B,C,D}\{A,B,C,D\}. A sequence is nonrepetitive if it contains no contiguous block of the form XXXX for a nonempty finite word XX, and palindrome-free if it contains no nonempty palindromic contiguous block. It avoids the subsequences CDCD and DCDC if neither of these occurs as a subsequence.

Sequence existence conjecture. There exists an infinite sequence on four letters, A,B,CA,B,C and DD such that the sequence is nonrepetitive, palindrome-free and avoids the subsequences CDCD and DCDC.

The paper states that this conjecture was recently confirmed by Kozik, so the existence claim is resolved.

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Sources & referencesView supporting material

Primary source

Balázs Keszegh, Balázs Patkós and Xuding Zhu, “Nonrepetitive colorings of lexicographic product of graphs”, arXiv:1210.5607 (2013).

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