python 求1-3！+5！-7！... .. ... .. . ... .（（-1）^（n-1））×（2n-1）!前N项和

[小 宝]

python 求1-3！+5！-7！... .. ... .. . ... .（（-1）^（n-1））×（2n-1）!前N项和

[chuifengde]

def pa(n):
    if n == 1:
        return 1
    else:
        return n * pa(n-1)
def pas(n):
    if n == 1 :
        return 1
    else:
        return pow(-1, n-1) * pa(2*n-1) + pas(n-1)
    
print(pas(4))

[小 宝]

引用 1 楼 chuifengde的回复:

def pa(n):
    if n == 1:
        return 1
    else:
        return n * pa(n-1)
def pas(n):
    if n == 1 :
        return 1
    else:
        return pow(-1, n-1) * pa(2*n-1) + pas(n-1)
    
print(pas(4))

蟹蟹！！！！

[阿麦]

已经算过的不再重算，节约一点。

def Hello(n):
	s = 1
	v = 1
	for x in range(1,n):
		v = -1 * v * (x+x) *(x+x+1)
		s = s + v
	return s

if __name__ == '__main__':
	n = 5
	print(n, Hello(n))