A finite von neumann ordinal.

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.