Find the number of switched remained on
Source: 2019 Jozsef Wildt International Math Competition-W. 28
May 18, 2020
puzzlecombinatorics
Problem Statement
In a room, we have 2019 aligned switches, connected to 2019 light bulbs, all initially switched on. Then, 2019 people enter the room one by one, performing the operation: The first, uses all the switches; the second, every second switch; the third, every third switch, and so on. How many lightbulbs remain switched on, after all the people entered ?