φ ( m , n , 0 ) = m + n , {\displaystyle \varphi (m,n,0)=m+n,\,\!} φ ( m , n , 1 ) = m ⋅ n , {\displaystyle \varphi (m,n,1)=m\cdot n,\,\!} φ ( m , n , 2 ) = m n , {\displaystyle \varphi (m,n,2)=m^{n},\,\!}