2 blue eyed people

	1st night, no one leaves
	2nd night, both blue eyed people realise the other one would have left if they couldn't see any other blue eyed people, so both know they have blue eyes, and both leave.
	
3 blue eyed people
	
	1st night, no one leaves
	2nd night, no one leaves - from each of their perspectives, the situation so far is consistent with the other two being the only ones with blue eyes
	3rd night, all three realise that the other two would have left if they could only see one other person with blue eyes, so all three know they must be the third person with blue eyes, and all three leave.
	
4 blue eyed people
	
	1st night, no one leaves
	2nd night, no one leaves - from each of their perspectives, the situation so far is consistent with the other three being the only ones with blue eyes
	3rd night, no one leaves - from each of their perspectives, the situation so far is consistent with the other three being the only ones with blue eyes
	4th night, all four realise the other three would have left if they could only see two other people with blue eyes, so all four leave.
	
100 blue eyed people

	100th night: all 100 blue eyed people leave