User blog comment:Undeadlift/Very Fast Growing Hierarchy/@comment-2A02:8108:4A40:A764:F8DF:6165:64B7:A588-20171025185148

Why not change the n + 1 of the first function to another definition like   n[n up-arrows]n. Apply the same rules as before, and every step is not just adding one, but putting an incredible amount of up-arrows between two huge numbers.