User blog comment:B1mb0w/Strong D Function/@comment-5529393-20150805054856/@comment-5529393-20150805083444

Well here's the thing - you can't just focus on one value of n in the fast-growing hierarchy, because the next level up will reference much larger variables. For example, say you've figured out what $$f_\phi(3)$$ is - will that determine what $$f_{\phi+1}(3)$$ is? No, because $$f_{\phi+1}(3) = f_\phi(f_\phi(f_\phi(3)))$$, so you need to figure out $$f_\phi(n)$$ is for $$n = f_\phi(f_\phi(3))$$, which is a gigantic number! So you need to deal with all n in parallel.

I will take a look at your other article.