Bracelet (combinatorics)

Bracelet (combinatorics)

In combinatorics, a "k"-ary bracelet of length "n" is the equivalence class of all "n"-character strings over an alphabet of size "k", taking reverse and all rotations as equivalent. A bracelet, also referred to as a turnover necklace, represents a structure with "n" circulary connected beads of "k" different colors, which (unlike a necklace) can be turned over.

There are:B_k(n) = egin{cases}{1over 2}N_k(n) + {1over 4}(k+1)k^{n/2} & mbox{if }nmbox{ is even} \ \{1over 2}N_k(n) + {1 over 2}k^{(n+1)/2} & mbox{if }nmbox{ is odd}end{cases}different "k"-ary bracelets of length "n", where N_k(n) is the number of "k"-ary necklaces of length "n".

See also

*Lyndon word

External links

* [http://www.theory.csc.uvic.ca/~cos/inf/neck/NecklaceInfo.html Info on necklaces, Lyndon words, De Bruijn sequences]


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