von Neumann integer
The von Neumann integer N is a finite set with N elements which are the von Neumann integers 0 to N-1. Thus
0 = {} = {}
1 = {0} = {{}}
2 = {0, 1} = {{}, {{}}}
3 = {0, 1, 2} = {{}, {{}}, {{}, {{}}}}
...The set of von Neumann integers is infinite, even though each of its elements is finite.
[Origin of name?]
