Python 递归计算分数数列

from fractions import Fraction


def fn(x):
    """
    计算每一项的值
    """
    time = 1
    fz = 2
    fm = 1
    if x == 1:return fz / fm
    #if x == 1:return Fraction(fz, fm) 这句话是分数表示
    else:
        while time < x :
            cost = fz + fm
            fm = fz
            fz = cost
            time = time + 1
        return fz / fm
        #return Fraction(fz, fm)

def sum_fn(x):
    """
    递归计算,进行函数每一项的相加
    """
    if x == 1:return 2
    else:
        return fn(x) + sum_fn(x-1)

a = int(input("请输入连续加到的项数："))
print(sum_fn(a))