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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.



