Knuth's up-arrow notation's requires an arrow symbol. Unlike exponentials, it cannot be written with only digits. I think you mean Goodstein's tetration notati

Knuth's up-arrow notation's requires an arrow symbol. Unlike exponentials, it cannot be written with only digits. I think you mean Goodstein's tetration notation. https://en.wikipedia.org/wiki/Tetration https://en.wikipedia.org/wiki/Tetration . ⁹9 is 9^(9^(9^(9^(9^(9^(9^(9^9))))))), if I counted it correctly. In the LinkedIn comments, one of the ones to mention this is Jeffry Nimeroff: > "I'm sorry but your daughter was wrong as well. And you were smarmy about it. If we allow exponentiation then we might as well allow tetration or further notions of super exponentiation. While I understand the point you are trying to make, at some point the common man principal takes over. Otherwise I can literally answer any question with any answer, just by changing my reference frame." I also concur with the comment by Alexander Doak: > No one is going to like me for this, but I call bull hockey on this story. It's FAKE. ... > 3.) Given the fact that everyone mentioned in the story was "wrong", and the alleged anguish, duration, effort, and expense that was put forth on the alleged correction, I would highly expect someone to bring up other operators which would produce larger numbers. But that was never mentioned. It certainly would have been if this story were real. Are we honestly to believe that multiple teams of math experts, teachers, writers, and lawyers just missed this critical, immediately evident fact? > 4.) I would like some additional sources for this apparent nation wide, sweeping event which caused everyone to get a 99 instead of 100 on some math tests. Give me some national coverage of this event, when it happened, who it affected, etc. Otherwise, the most important parts of this story (if not the whole story) is just fakity fake, fake.