And so he said, if you start off with a male and a female, at the end of one month they have an offspring. Let's assume they have two offspring. At the end of the next month let's assume those offspring have offspring. Again a male and female.

在13世纪的时候想要计算兔子的数量,就是一个月大的兔子,再过一个月就可以进行交配,所以它说如果你一开始有一公一母两只兔子,在一个月末它们就可以生小兔子,让我们假设它们生了两只小兔子。

麻省理工公开课 - 计算机科学及编程导论课程节选