Example
181
[291]In this model, the first natural number \(0\) is identified with \(β \). Then
\begin{align*} 1& = 0 βͺ \{ 0\} = \{ 0\} = \big\{ \{ \} \big\} ,\\ 2& = 1 βͺ \{ 1\} = \{ 0, 1\} = \Big\{ \{ \} , \big\{ \{ \} \big\} \Big\} ,\\ 3& = 2 βͺ \{ 2\} = \{ 0, 1, 2\} = \bigg\{ \{ \} , \big\{ \{ \} \big\} , \Big\{ \{ \} , \big\{ \{ \} \big\} \Big\} \bigg\} ,\\ .... \end{align*}