Light Em up

Consider n light bulbs of the same color in a row. Given that some of them could be lit up at the same time, how many different orders are there for the bulbs to be lit up?

Example:-
If there are 2 bulbs so the required permutations will be-
1) when both bulbs are switched on together.
2) when first bulb is switched first and second bulb is switched on after it.
3) when second bulb is switched first and the first bulb is switched later.
Hence the required number of permutations are 3 for 2 bulbs.