有一个分数序列1/2,2/3,3/5,5/8,8/13,13/21......求这个序列的前20项之和。帮忙啊！C语言编程

#include main() { double a[20],b[20]; int i=0; double sum=0; a[0] = 1; b[0] = 2; a[1] = 2; b[1] = 3; for (i=2;i<20;i++) { a[i] = a[i-2] + a[i-1]; b[i] = b[i-2] + b[i-1]; } for (i=0;i<20;i++) { sum += a[i]/b[i];