The pattern is as follows:

2, 6, 12, 20.

For each tower, we can see we have the X^{2} + X * - where X is the tower number.*

So, let's say it was the 3rd tower.

So, substituting for the equation, we get:

3^{2} + 3 = 12

If we check, that is true. The 3rd tower does have 12 blocks.

**Let's find the total for the 99th tower.**

Total = 99^{2} + 99 = 9900

Therefore, the 99th tower has 9900 blocks.

(Solved by a 12 y/o)