Earlier quoted context omitted.
I always assumed that intuitively... I think the number is 20 people for the birthday paradox. 20 x 20 = 400, and there are ~365 days in a year. Is that how that works?
I was always surprised the math maths for birthdays. Human birthdays are not random, and cluster around various dates and seasonal patterns.
Doesn't the clustering make collisions strictly more likely?