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CIIM 2015 Problem 5

Source:

August 9, 2016
CIIM 2015undergraduatefunction

Problem Statement

There are nn people seated on a circular table that have seats numerated from 1 to nn clockwise. Let kk be a fix integer with 2kn2 \leq k \leq n. The people can change their seats. There are two types of moves permitted:
1. Each person moves to the next seat clockwise. 2. Only the ones in seats 1 and kk exchange their seats.
Determine, in function of nn and kk, the number of possible configurations of people in the table that can be attain by using a sequence of permitted moves.