PLEASE HELP ME! A clerk in the sports department of a store is stacking tennis balls in the shape of a square pyramid. The top layer has 1 ball, the second layer has 4 balls, the third layer has 9 balls, and so on, as shown below.
Which of the following represents the number of balls in the first 8 layers of the pyramid?
a series that is arithmetic
a series that is geometric
a series that is neither arithmetic nor geometric
a series cannot be used to represent this situation.