The Dirty Path

Bob is currently at origin. Bob walks on $X$-axis and towards the right. In one move, Bob can either jump 1 unit to the right or 2 units to the right. Some of these coordinates are dirty. Bob wants to know the number of ways going to $(Y, 0)$ from $(0, 0)$. Two ways are considered to be different if there exists an integer $j$ such that the location of Bob after $j$ steps is different. Sounds l