一道PP的题，求翻译

xiaoping0000

Is the integer n odd ？

1) n is divisible by 3

2) 2n is divisible by twice as many positive integers as n

B

第二个条件啥意思？

SHJDHKBB9

应该是2n有|2n|个因子.

entheticism

我看第二个条件是说
2n能被n这么个正整数除两次。这说明2n/n=2 2\n=还是整数
说的是divisible 所以排除1，那n只能是2，不是奇数，所以选择b。

pastnow

还真不懂说的什么，同问

smiling_cd

以下是引用SHJDHKBB9在2009-1-18 22:22:00的发言：
应该是2n有|2n|个因子.

欧也觉得是这个

lionelee

It means if n is divisible by x (个) intergers, then 2n is divisible by 2x (个) intergers.

xiaoping0000

以下是引用pastnow在2009-1-19 4:09:00的发言：
还真不懂说的什么，同问

感谢，终于明白了。看到老美的解释。

If n is even --- 2n will not have twice as many divisors as n
e.g . For n=2; 2n or 4 has 1,2,4 as divisors ,
For n = 4 divisors are 1,2,4; 2n=8 has 1,2,4,8

But if n is odd
then if n=3 divisors are 1,3 and 2n=6 divisors are 1,2,3,6
n=5 divisors are 1,5 and 2n=10 divisors are 1,2,5,10

Thus if n is odd the 2nd condition is satisfied. Hence ans is B