Okay I am just starting to get somewhere.
I am looking at how many ways even numbers of people can be paired off
This post is NOT directly related to the question above.
4 people ABC and D
AB CD
AC BD
AD BC
that is 4 people can be paired off in 3 ways
Now, before I wanted to do it as 4C2 which is 6
This would give the 6 above but each time you get one pair you automatically get the another pair so it can be seen that this will be too big by a factor of 2 so it is 4C2/2 = 6/2=3
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6 People
Now I am going to look at 6 people A B C D E and F
AB there are four more so they can be paired up 3 ways
AC 3 ways
AD 3 ways
AE 3 ways
AF 3 ways
Total = 3*5 =15
So 6 people can be paired off 15 ways. This is (6-1)(4C2)/2 = 15
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8 People
Now I am going to look at 8 people A B C D E F G and H
AB then 6 more = 15 ways
AC then 6 more = 15 ways
AD then 6 more = 15 ways
AE then 6 more = 15 ways
AF then 6 more = 15 ways
AG then 6 more = 15 ways
AH then 6 more = 15 ways
That is a total of 7*15=105 (8-1)(6-1)4C2/2 = 7*5*3
that is 8 people can be paired off in 105 ways
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So 2K people can be paired off in 3*5*7*......*(2K-1) ways
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So 4 people are paired (and the pairs are then considered as 1)
they are then put clockwise into a cirlce (or anticlockwise) rotations are considered the same.
The number of ways this could be done is 4*1=4 ways
6 people - it could be done 5*3*2! = 30 ways
8 people - it could be done 7*5*3*3! = 1050 ways
2K people - it could be done (2k-1)(2k-3)....5*3*(k-1)!
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