选择题
2022 AMC 8 Problem 17: Double Factorial Sum
If n is an even positive integer, the double factorial notation n!! represents the product of all the even integers from 2 to n. For example, 8!! = 2 · 4 · 6 · 8. What is the units digit of the following sum?
2!! + 4!! + 6!! + ⋯ + 2018!! + 2020!! + 2022!!
2022 AMC 8 第17题：双阶乘和
如果 n 是偶正整数，则双阶乘符号 n!!表示从 2 到 n 的所有偶数的乘积。例如，8！ = 2 · 4 · 6 · 8. 下列和的个位数是多少
2!! + 4!! + 6!! + ⋯ + 2018!! + 2020!! + 2022!!
A.
0
B.
2
C.
4
D.
6
E.
8