Uriel Function

基本规则：

${{𝒰}}_0(n)=n+1$

${{𝒰}}_{\alpha }(n)=\underset{n\text{ times}}{\underbrace{{{𝒰}}_{\alpha -1}({{𝒰}}_{\alpha -1}(\dots {{𝒰}}_{\alpha -1}(n)\dots ))}},\alpha <\omega$

${{𝒰}}_{\omega }(n)={{𝒰}}_n({{𝒰}}_{n-1}(n-1))$

${{𝒰}}_{\omega +m}(n)={{𝒰}}_{\omega +m-1}^{{{𝒰}}_{\omega +m}(n-1)}(n)$

${{𝒰}}_{{\omega }^2}(n)={{𝒰}}_{\omega \cdot {{𝒰}}_{{\omega }^2}(n-1)}^{{{𝒰}}_{{\omega }^2}(n-1)}(n)$