Many people emailed me this apparent paradox showing 4 = 2. Can you figure out where the mistake is?

My blog post for this video
https://wp.me/p6aMk-80Q

Award winning paper Knoebel, R. Arthur. "Exponentials reiterated." The American Mathematical Monthly 88.4 (1981): 235-252.
http://www.maa.org/programs/ma....a-awards/writing-awa

Wikipedia tetration
https://en.wikipedia.org/wiki/....Tetration#Extension_

False proof 2 equals 4
https://jeremykun.com/2012/05/....05/false-proof-2-4-a

Math StackExchange links
https://math.stackexchange.com..../questions/87870/are
https://math.stackexchange.com..../questions/108288/in

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