Python | sympy .阶乘 2()方法

原文:https://www . geesforgeks . org/python-sympy-factorial 2-method/

借助因子 2() 方法，我们可以找到双因子。数字的双阶乘由–

n!! = \begin{cases} 1 & n = 0 \ n(n-2)(n-4) \cdots 1 & n\ \text{positive odd} \ n(n-2)(n-4) \cdots 2 & n\ \text{positive even} \ (n+2)!!/(n+2) & n\ \text{negative odd} \end{cases}

语法:阶乘 2(n)

参数: n–表示要计算双阶乘的数。

返回:返回数字的双阶乘，即 n。

示例#1:

# import sympy 
from sympy import * 

n = 10
print("Value of n = {}".format(n))

# Use sympy.factorial2() method 
factorial2_n = factorial2(n)  

print("Double factorial of n : {}".format(factorial2_n))  

输出:

Value of n = 10
Double factorial of n : 3840

例 2:

# import sympy 
from sympy import * 

n = -3
print("Value of n = {}".format(n))

# Use sympy.factorial2() method 
factorial2_n = factorial2(n)  

print("Double factorial of n : {}".format(factorial2_n))  

输出:

Value of n = -3
Double factorial of n : -1

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