"Ahu" are stone platforms on which many moai sit. There are 313 known ahu and 125 of these carry moai. The biggest, Ahu Tongariki is 220 m (720 ft), and had the most (15) and tallest moai.
I don't know how many thoughts we have a second, but it's quite an amazing number, and just to pin down the appropriate sequence of those, all you really need is a pencil and a piece of paper.