n cells occupied by 0 or 1 arranged into a circle
Source: Austrian Polish 1981 APMC
April 30, 2020
combinatorics
Problem Statement
Let cells be arranged into a circle. Each cell can be occupied by or . The following operation is admissible: Choose any cell occupied by a , change it into a and simultaneously reverse the entries in the two cells adjacent to (so that become , ). Initially, there is a in one cell and zeros elsewhere. For which values of is it possible to obtain zeros in all cells in a finite number of admissible steps?