There are light bulbs installed across an infinitely long hallway. Initially all the light bulbs are off. The first person that walks through the hallway, turns on every light bulb. The 2nd person that walks through the hallway, changes the status of every 2nd light bulb, the 3rd person that walks through the hallway changes the status of every 3rd light bulb (so in essence, he turns off the 3rd light bulb - initially it is off, 1st person turns it on, 2nd person does not touch it, 3rd person changes the status -> turns it off). 4th person walking though the hallway, changes the status of every 4th bulb and so on. Infinite numbers of people walk through this hallway.
At the end of the process, which light bulbs will be on?