Abstract
Given a set S of words, let \(S^\dagger \) denote the iterated shuffle of S. We characterize the finite sets S for which \(S^\dagger \) is co-finite, and we give some bounds on the length of a longest word not in \(S^\dagger \).
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Notes
There is no standard notation to denote the iterated shuffle; we are following Jantzen’s use of the “dagger”.
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Communicated by Markus Lohrey.
J. Nicholson: was supported by an NSERC USRA. N. Rampersad: was supported by NSERC Discovery Grant No. 418646–2012.
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Nicholson, J., Rampersad, N. The Frobenius problem for the shuffle operation. Semigroup Forum 96, 160–177 (2018). https://doi.org/10.1007/s00233-017-9867-4
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DOI: https://doi.org/10.1007/s00233-017-9867-4