Answer: n^2 + 1
Explanation:
Imagine that you cross out the top-most square for each step of each diagram. The squares not crossed out have the following counts: 1, 4, 9
This is the sequence of perfect squares. So the rule will have us take the number n, and square it to get n^2. Then we add on the squares we crossed out earlier. This explains the "plus 1" at the end to get the answer of n^2+1
