This tests how many of the unnamed tropical fish in Minecraft you have to go through until you have collected all the (2700) types, to experimentally confirm that this is on average equal to the product of 2700 and the 2700th harmonic number (8.478...). This is indeed true. You can change the fish type count before starting to experiment, and hold z or x to slow down the process at different speeds.
This relates to the harmonic numbers, as the total number of fish looked at until you've seen all the unique fish on average is expected to be equal to 2700 * H2700, i.e. the 2700th harmonic number, roughly 8.478.
