A bijection between necklaces and multisets with divisible subset sum
The electronic journal of combinatorics, Tome 26 (2019) no. 1
Consider these two distinct combinatorial objects: (1) the necklaces of length $n$ with at most $q$ colors, and (2) the multisets of integers modulo $n$ with subset sum divisible by $n$ and with the multiplicity of each element being strictly less than $q$. We show that these two objects have the same cardinality if $q$ and $n$ are mutually coprime. Additionally, when $q$ is a prime power, we construct a bijection between these two objects by viewing necklaces as cyclic polynomials over the finite field of size $q$. Specializing to $q=2$ answers a bijective problem posed by Richard Stanley (Enumerative Combinatorics Vol. 1 Chapter 1, Problem 105(b)).
@article{10_37236_7804,
author = {Swee Hong Chan},
title = {A bijection between necklaces and multisets with divisible subset sum},
journal = {The electronic journal of combinatorics},
year = {2019},
volume = {26},
number = {1},
doi = {10.37236/7804},
zbl = {1409.05030},
url = {http://geodesic.mathdoc.fr/articles/10.37236/7804/}
}
Swee Hong Chan. A bijection between necklaces and multisets with divisible subset sum. The electronic journal of combinatorics, Tome 26 (2019) no. 1. doi: 10.37236/7804
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