题目

Play is the basic business of childhood, and in recent years research has shown the great importance of play in the development of a human being．From earliest infancy （婴儿）, every child needs opportunity and right materials for play, and the main tools of play are toys．The main function of toys is to suggest, encourage and play．To succeed in this, they must be good toys, which children will play with often, and will come back again and again．Therefore, it is important to choose suitable toys for different stages of a child’s development．        In recent years research1，1，2，3，5，8，13，…这一列数的规律是：第1，第2个数是1，从第3个数起，该数是其前面2个数之和．试编写一个程序，计算这列数中前20个数之和．