If you need a new headache...

[Audi Driver P.E.]

Perhaps you have plenty.  Perhaps you're even familiar with this already.  Have you heard of Kruskal's tree theorem?  Oh it's a read.  Wrap your head around this:

tree(1) = 2, tree(2) = 5, and tree(3) > 262140, but TREE(3) is larger than treetreetreetreetree8(7)(7)(7)(7)(7).

 

[wilheldp_PE]

I read the Wikipedia article and I'm no closer to comprehending what its trying to say than I would be if it were written in Swahili.  Not only do I not understand what a tree is in this context, but I have no idea what reverse mathematics or ATR is (after reading their Wiki articles).

 

[kevo_55]

Headache? I can't even read half of those superscripts.

 

[Supe]

Tree = fiddy

 

[Dleg]