Trienn

The triennet is equal to \(\lbrace9,9,9\rbrace\) or \(9\lbrace9\rbrace9\) in BEAF or 9 undecated to 9. . The term was coined by Aarex Tiaokhiao. This is the ninth Ackermann number.

Etymology
The name of this number is based on tri- (three) and ennea- (nine), meaning that there are 3 9's in the array.