1) 1,5,7,11. 4) (2n-1)!!

这两题都不错，不太难，而且比较好玩

所有跟帖： 

• 从总和60也可以凑出1,11,19,20.　不怎么证４是最大的。 -wxcfan123- ♂ (0 bytes) () 08/02/2011 postreply 18:31:45

• OPPS. 1,11, 19, 29 -wxcfan123- ♂ (0 bytes) () 08/02/2011 postreply 18:33:21

• 回复：从总和60也可以凑出1,11,19,20.　不怎么证４是最大的。 -康MM- ♀ (123 bytes) () 08/03/2011 postreply 04:37:41

• Thx. -wxcfan123- ♂ (0 bytes) () 08/03/2011 postreply 09:51:42

• KMM's Q is wonderfer.I tellyou the detail. -jinjing- ♀ (399 bytes) () 08/03/2011 postreply 15:07:21

• Key point is a1+a4-a2+a3. -jinjing- ♀ (0 bytes) () 08/03/2011 postreply 05:28:08

• 回复：Key point is a1+a4=a2+a3. -jinjing- ♀ (0 bytes) () 08/03/2011 postreply 05:29:18

• Are you sure for 4) n=3 seems not right. -jinjing- ♀ (0 bytes) () 08/02/2011 postreply 20:55:24

• Proof of 4. It is fun. -wxcfan123- ♂ (649 bytes) () 08/03/2011 postreply 08:27:10

• let me show U, fn=(n+1)!/2. I'm right,MM is... -jinjing- ♀ (469 bytes) () 08/03/2011 postreply 12:48:41

• Jingling, your answer is obviously wrong. Wxc's proof is beautif -乱弹- ♂ (238 bytes) () 08/04/2011 postreply 10:06:43

• How are you,Ｍy answer is right is right,though my right side is -jinjing- ♀ (173 bytes) () 08/04/2011 postreply 13:32:34

• my right side is Q's left side, -jinjing- ♀ (0 bytes) () 08/04/2011 postreply 13:35:51

• 唉，怎么说呢。N=3，见内。 -wxcfan123- ♂ (295 bytes) () 08/04/2011 postreply 14:09:00

• Thx,your right,I am sorry ,My answer is for last states.not求整个操作 -jinjing- ♀ (29 bytes) () 08/04/2011 postreply 14:30:48

• My solution, it is not Dct. -jinjing- ♀ (226 bytes) () 08/04/2011 postreply 18:07:45

• Your (n-1)! * 2^{n-1}is not right, should be n!, n=3,first is he -jinjing- ♀ (22 bytes) () 08/04/2011 postreply 14:11:09

• I am sorry ,My answer is for last states.not求整个操作过程的不同方法个数． -jinjing- ♀ (0 bytes) () 08/04/2011 postreply 14:27:34

• A={a1,5a1,7a1,11a1} is the answer. -jinjing- ♀ (0 bytes) () 08/03/2011 postreply 10:06:39

• 4)：A={a1,5a1,7a1,11a1}and A={a1,11a1,19a1,29a1} a1 cantake any -jinjing- ♀ (0 bytes) () 08/03/2011 postreply 15:16:48