hehe, funny, I just caught on to that (see edit above).

It's pretty logical really, but I can't seem to come up with what it should work out to. But the notation, once you go from ^ for exponentiation to ^^ for tetration immediately suggests ^^^ for the next step. I feel pretty dumb now for not realizing right away that was what was intended. (edit: I suck at math, in case that wasn't clear yet...).

Thanks!