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ENUMERATING NECKLACES WITH TRANSITIONS

Published online by Cambridge University Press:  11 May 2021

FRANCESCO BIANCONI*
Affiliation:
Department of Engineering, Università degli Studi di Perugia, Via Goffredo Duranti 93, 06125 Perugia, Italy
EMANUELE BRUGNOLI
Affiliation:
Communications Regulatory Authority (AGCOM), Centro Direzionale Isola B5, Naples, Italy e-mail: brugnoliema@gmail.com
*

Abstract

Necklaces are the equivalence classes of words under the action of the cyclic group. Let a transition in a word be any change between two adjacent letters modulo the word’s length. We present a closed-form solution for the enumeration of necklaces in n beads, k colours and t transitions. We show that our result provides a more general solution to the problem of counting alternating (proper) colourings of the vertices of a regular n-gon.

Type
Research Article
Copyright
© 2021 Australian Mathematical Publishing Association Inc.

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Footnotes

Partially supported by the Department of Engineering, Università degli Studi di Perugia, Italy, within the project Artificial Intelligence for Earth Observation (Fundamental Research Grant Scheme 2020).

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