46. Nancy assembles a heap of tennis balls. She makes a first layer on level grounds. Figure 1 shows the top perspective on her first layers.
She then forms the subsequent layer, putting the initial three balls as appeared in Figure 2.
Each ball rests in the empty between four balls in the layer underneath .
Nancy keeps constructing the stack similarly, making whatever number layers as could be allowed.
How many ball are used altogether in the completed stack?