User blog comment:Primussupremus/The X number./@comment-28606698-20170321190454

You are still at omega+1 level:

$$\text{X-number}\approx f_{\omega+1}(\text{Gogolplex})$$

since $$x_{x_0}=\text{X-number}$$, where

$$x_0=10^{10^{100}}$$

$$x_{k+1}=x_k\uparrow^{x_k}x_k$$