The number of prefixes of minimal factorisations of a cycle
The electronic journal of combinatorics, Tome 23 (2016) no. 3
We prove in two different ways that the number of distinct prefixes of length $k$ of minimal factorisations of the $n$-cycle $(1\ldots n)$ as a product of $n-1$ transpositions is $\binom{n}{k+1}n^{k-1}$. Our first proof is not bijective but makes use of a correspondence between minimal factorisations and Cayley trees. The second proof consists of establishing a bijection between the set which we want to enumerate and the set of parking functions of a certain kind, which can be counted by a standard conjugation argument.
DOI :
10.37236/4799
Classification :
05C38, 05C70, 05C25, 05A18
Mots-clés : factorisation of cycles, non-crossing partitions, parking functions
Mots-clés : factorisation of cycles, non-crossing partitions, parking functions
Affiliations des auteurs :
Thierry Lévy  1
@article{10_37236_4799,
author = {Thierry L\'evy},
title = {The number of prefixes of minimal factorisations of a cycle},
journal = {The electronic journal of combinatorics},
year = {2016},
volume = {23},
number = {3},
doi = {10.37236/4799},
zbl = {1344.05079},
url = {http://geodesic.mathdoc.fr/articles/10.37236/4799/}
}
Thierry Lévy. The number of prefixes of minimal factorisations of a cycle. The electronic journal of combinatorics, Tome 23 (2016) no. 3. doi: 10.37236/4799
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