题目:有一分数序列:2/1,3/2,5/3,8/5,13/8,21/13...求出这个数列的前20项之和。
package cn.ls.lanqiao;
import java.util.*;
public class Test20 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
float a = 1;
float b = 2;
float sum = 0;
float t;
for (int i = 1; i <= n; i++) {
sum += b / a;
t = a;
a = b;
b = a + t;
}
System.out.println(sum);
}
}