有一对兔子，从出生到第三个月起每个月都生一对兔子，小兔子长到第三个月后每一对又生一对兔子，加入兔子不死问每个月的兔子总数为多少(A pair of rabbits gave birth to a pair of rabbits every month from birth to third months. When the rabbit grew to third months, each pair gave birth to a pa