Python基础问题Sn=1-3+5-7+9...请问大家我怎么改是对的

Question

请问这个该怎么写，我怎么改，或者有没有更好的方法，谢谢大家的帮助。

Answer 1

Sn = 0
an = 0
bn = 0
n = int(input('请输入n：'))
for a in range(1, n+1):
    if a % 2 != 0:
        an = 2 * a - 1
        bn = 0
    else:
        bn = 2 * a - 1
        an = 0
    Sn += (-1) ** (a-1) * (an + bn)
print("Sn = ", Sn)