Guichard-Combinatorics-Graph-Theory · Problem 2.2.11
Inclusion-Exclusion
Mathematics — Probability · derangements-seating
Problem
Suppose n people are seated in m≥n chairs in a room. At some point there is a break, and everyone leaves the room. When they return, in how many ways can they be seated so that no person occupies the same chair as before the break?