It's the y intercept.
If y = a then every point on the line would be (x,a)
The lines slope is 0. I know that has nothing to do with the question, but it is true and it gives me 3 things to tell you.
3 to the power of 1 simplified, is just 3.
It's a geometric sequence.

It's the sum for term 4 through term 15.
Where is this at?
Could you send it in comments here or something?
It will take 49 minutes for 9 people to paint 7 walls