MathDB
BMT 2013 Spring - Discrete 10

Source:

January 6, 2022
combinatorics

Problem Statement

Let σn\sigma_n be a permutation of {1,,n}\{1,\ldots,n\}; that is, σn(i)\sigma_n(i) is a bijective function from {1,,n}\{1,\ldots,n\} to itself. Define f(σ)f(\sigma) to be the number of times we need to apply σ\sigma to the identity in order to get the identity back. For example, ff of the identity is just 11, and all other permutations have f(σ)>1f(\sigma)>1. What is the smallest nn such that there exists a σn\sigma_n with f(σn)=kf(\sigma_n)=k?