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Counting colorful necklaces and bracelets in three colors

  • Dennis S. Bernstein
  • Omran KoubaEmail author
Article
  • 9 Downloads

Abstract

A necklace or bracelet is colorful if no pair of adjacent beads are the same color. In addition, two necklaces are equivalent if one results from the other by permuting its colors, and two bracelets are equivalent if one results from the other by either permuting its colors or reversing the order of the beads; a bracelet is thus a necklace that can be turned over. This note counts the number K(n) of non-equivalent colorful necklaces and the number \(K'(n)\) of colorful bracelets formed with n-beads in at most three colors. Expressions obtained for \(K'(n)\) simplify expressions given by OEIS sequence A114438, while the expressions given for K(n) appear to be new and are not included in OEIS.

Keywords

Group action Burnside’s lemma Necklace Bracelet Periodic three color sequences 

Mathematics Subject Classification

05A05 

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Notes

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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Department of Aerospace EngineeringThe University of MichiganAnn ArborUSA
  2. 2.Department of MathematicsHigher Institute for Applied Sciences and TechnologyDamascusSyria

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