Another coin problemNumber Theory Level 4
There \(1000\) coins placed in a line, and each one is facing up. A man flips every other coin, going down the line from left to right. He then starts on the left and flips every third coin, then flipping every fourth, and so on until he has gone down the line \(999\) times. How many coins are facing up at the end?
(This problem is not original)