please help me with this word problem , first answer get points?

[Mellissa]

On the ancient island of Circulus archaeologists found a series of caves. In the first cave they found a circle with 560 stones. In the second cave they found a circle of stones with 8 fewer stones than in the first cave. Each new cave had a circle with twice as many stones missing from the circle than in the previous cave. For example, in the third cave there were 16 fewer stones in the circle than in the second cave. If the stone circles continued in this way, which cave would have the last stone circle