python 100题24

python 100题24

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。

a = 1 
i = 1
k = 0 #i + a
count = 0 #统计分数序列之和
f = 0 # i / a
count_times = 1 #执行次数
while count_times <= 20:
    k = i + a
    a = i
    i = k
    f = i / a
    count += f
    count_times += 1
print("前20项和：",count)