In Conway chained arrow notation, I understand chains of three, for example: 2 -> 3 -> 3 = 2^^^3 (using Knuth up-arrow notation), but I haven't been able to understand how chains of four work. I got from Wikipedia that 3 -> 2 -> 2 -> 2 = 3 -> 3 -> 8, but I don't understand how exactly. What does the fourth number do to the rest of the chain? Can any of you smart math people (serpicojr) enlighten me?