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Israel 2015 Q6 - Shifting lamps process

Source: Israel National Olympiad 2015 Q6

August 7, 2019
combinatoricsProcesseslamps

Problem Statement

Let n1n\geq1 be a positive integer. nn lamps are placed in a line. At minute 0, some lamps are on (maybe all of them). Every minute the state of the lamps changes: A lamp is on at minute t+1t+1 if and only if at minute tt, exactly one of its neighbors is on (the two lamps at the ends have one neighbor each, all other lamps have two neighbors).
For which values of nn can we guarantee that all lamps will be off after some time?