20000以下只有2262个质数，而且这个节目实际上是从1000到20000，而且有1/3是偶数，不知道难度在哪？

所有跟帖： 

• 我也觉得这个挑质数没那么难吧。 尤其最后加试题 -Joyyu- ♀ (465 bytes) () 01/11/2015 postreply 03:51:05

• Divisibility by 3 Rule Rule: A number is divisible by 3 if the -Joyyu- ♀ (128 bytes) () 01/11/2015 postreply 03:55:04

• Divisibility by 4 Rule Rule: A number is divisible by 4 if the -Joyyu- ♀ (138 bytes) () 01/11/2015 postreply 03:56:50

• Divisibility by 6 Rule Since 6 is a multiple of 2 and 3, the ru -Joyyu- ♀ (269 bytes) () 01/11/2015 postreply 03:58:13

• Divisibility by 8 Rule Rule A number passes the test for 8 if t -Joyyu- ♀ (142 bytes) () 01/11/2015 postreply 04:00:22

• 加试题8771 很容易阿， even number ， 5全排除， -Joyyu- ♀ (268 bytes) () 01/11/2015 postreply 04:20:18

• 1843是素数还是合数？19*97.除了考虑能否被2，3，5，7整除外，还要考虑11，13，17等等整除 -阿点- ♂ (0 bytes) () 01/16/2015 postreply 15:36:39