User blog comment:Primussupremus/Omicron number./@comment-1605058-20170417181746/@comment-28606698-20170417185840

We can define simple rule

$$\Omega[\eta]=\eta$$

and then

$$f_{\Omega}(3)=f_{\Omega[3]}(3)=f_{\omega[3]}(3)=f_3(3)=6.89508 \times 10^{121210694}$$

but this is much smaller than $$f_{\psi(\Omega)}(3)$$.

Depending to definition of psi-function it can be equal to $$f_{\varepsilon_0}(3)$$ or $$f_{\zeta_0}(3)$$ etc. and in this we should  define more rules for fundamental sequences.