User blog comment:Wythagoras/BEAF:structures and ordinals/@comment-1605058-20131210201100/@comment-25418284-20131211220048

@Wythagoras Oops, right, what was I thinking.

@LittlePeng But \(\omega \uparrow (\omega \uparrow\uparrow \omega) = \omega \uparrow\uparrow \omega\), because \(\varepsilon_0 = \omega^{\varepsilon_0}\)! The standard definition of tetration has to be modified for ordinals.