User blog comment:Mush9/zz Function/@comment-24920136-20161025230641

Warning, infinite loop detected.

zz(a,b+1), initial substitution

= 3^..zz(a,b)...^(zz(zz(...,b),b)) where ... = (zz(zz(...,b),b))

second substitution

= 3^..zz(a,b)...^(zz(zz((zz(zz(...,b),b)),b),b)) where ... = (zz(zz(...,b),b))

third substitution

= 3^..zz(a,b)...^(zz(zz((zz(zz((zz(zz(...,b),b))b),b)),b),b)) where ... = (zz(zz(...,b),b))

it never terminates