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Topic: 2 fold derangements
Replies: 0

 Patrick D. Rockwell Posts: 57 Registered: 12/12/04
2 fold derangements
Posted: Jul 2, 2013 12:46 AM

Could someone please help me with the subject covered on the following url?

http://www.mathpages.com/home/kmath430.htm

It's about something called two fold derangements.

I think that a two fold derangements is a derangement of two other arrangements such as the following.

12345
34521

41253 <-----------

Notice that the third line has numbers. that are different from the ones above, but I wonder if the author of the above URL has
another idea because he comes up with different numbers than I do.

Also, what does the following signify?

[1][1][1][1][1]
[1][1][1][2]
[1][1][3]
[1][2][2]
[1][4]
[2][3]
[5]

For example, does [2][3] signify an arrangement where 2 elements are the same,
and the other 3 are different from them but identical to each other?

Thanks in advance for any help.