Question

用JAVA求1+1+2+3+5+8+13+21的和

Answer 1

 public static void main(String[] args) {                   double sum = 0;                   int n = 1;                   int m = 1;                   int j;                   for(int i=1; i<=20; i++) {                          sum = sum + m/(double)(m+n);                          j = m;                           m = m+n;                          n = j;                   }                 System.out.println("sum=" + sum);              }

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Answer 2

sn=a1+a2+a3+...an

sn=a2+a3+...+an+a1
2sn=a3+a4+...a(n+1) + an + a1
2sn=sn-a2+a(n+2)
sn=a(n+2)-a2
额，所以你只要再继续算后两项，然后减去第二项1就行了
这里就是13+21+21=55 然后55-1=54