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。

c复制代码
 #include <stdio.h>  
 
   
 
 int main() {  
 
     double sum = 0.0;  
 
     int numerator = 2, denominator = 1;  
 
     for (int i = 0; i < 20; i++) {  
 
         sum += (double)numerator / denominator;  
 
         int nextNumerator = numerator + denominator;  
 
         denominator = numerator;  
 
         numerator = nextNumerator;  
 
     }  
 
     printf("The sum of the first 20 terms is: %.15f\n", sum);  
 
     return 0;  
 
 }

c复制代码
 #include <stdio.h>  
 
   
 
 typedef struct {  
 
     int numerator;  
 
     int denominator;  
 
 } Fraction;  
 
   
 
 Fraction getNextFraction(Fraction f) {  
 
     Fraction next;  
 
     next.numerator = f.numerator + f.denominator;  
 
     next.denominator = f.numerator;  
 
     return next;  
 
 }  
 
   
 
 double sumFractions(int n) {  
 
     double sum = 0.0;  
 
     Fraction f = {2, 1};  
 
     for (int i = 0; i < n; i++) {  
 
         sum += (double)f.numerator / f.denominator;  
 
         f = getNextFraction(f);  
 
     }  
 
     return sum;  
 
 }  
 
   
 
 int main() {  
 
     printf("The sum of the first 20 terms is: %.15f\n", sumFractions(20));  
 
     return 0;  
 
 }

python复制代码
 def sum_fractions(n):  
 
     numerator, denominator = 2, 1  
 
     total_sum = 0.0  
 
     for _ in range(n):  
 
         total_sum += numerator / denominator  
 
         numerator, denominator = numerator + denominator, numerator  
 
     return total_sum  
 
   
 
 print(f"The sum of the first 20 terms is: {sum_fractions(20)}")

python复制代码
 def fraction_generator(n):  
 
     numerator, denominator = 2, 1  
 
     for _ in range(n):  
 
         yield numerator / denominator  
 
         numerator, denominator = numerator + denominator, numerator  
 
   
 
 def sum_fractions(n):  
 
     return sum(fraction_generator(n))  
 
   
 
 print(f"The sum of the first 20 terms is: {sum_fractions(20)}")