There are 2 ^ n subsets, 2 ^ n-1 nonempty subsets and 2 ^ n-2 nonempty proper subsets of set a with n elements What if n = 0

There are 2 ^ n subsets, 2 ^ n-1 nonempty subsets and 2 ^ n-2 nonempty proper subsets of set a with n elements What if n = 0

The natural number n ≥ 1 is required here
If n = 0, then there is no element, that is, an empty set
There are no subsets, nonempty subsets and nonempty proper subsets in an empty set