Calculate the sum of sequences

1. Problem description

There's a sequence of scores ：2/1,3/2,5/3,8/5,13/8,21/13... Find the front of this sequence 20 Sum of items .

Example ：

Input ： Enter the first twenty , And take two decimal places .

Output ：32.66

2. Algorithm description

Given two starting numbers , Assign values respectively , Then put it into the loop , According to the law , The numerator is the last group of numerators and the denominator , Concurrent recurrence , Until item 20 , Finally, sum , The results of .

3. Experimental discussion and results

Find out the rules , And write a cycle according to the law , Then write the program .

a=1 b=2 s=0 for I  in range(1,21):    s+=b/a    a , b=b ,  b +a print(s) print('=%.2f'%s)

Four . Conclusion

The main consideration of this problem is to find out the rules of numerator and denominator , And put it into the loop , Calculate and get the result .