Arithmetic means they increase(or decrease!) by common number. 1,2,3,4, is an example because they increase by ones every time.
Geometric means that it increases (or decreases!) by a common RATIO, such as 1,2,4,8 with the common ratio of 2.
There is no way for it to be both, notice.
Without the following series, I can't really help.
If this enlightened you, please give brainliest answer, rate, and thank!