Bulbs

There are n bulbs in a row lighted during a marriage ceremony. A mischievous boy was passing from nearby when he had a naughty idea of breaking the bulbs. To make it interesting he does so in a pattern. He decides to smash every second lighted bulb on his first traversal, every third lighted bulb on his second traversal and so on. Getting exhausted at end he found that some of the bulbs remain luc