12 numbered chairs arranged in a circle
Source: 2019 Dürer Math Competition Finals Day2 E+13 https://artofproblemsolving.com/community/c1621835_2019_
January 5, 2022
combinatorics
Problem Statement
There are chairs arranged in a circle, numbered from to . How many ways are there to select some of the chairs in such a way that our selection includes consecutive chairs somewhere?