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Can anyone find the sequence with this rule:
Find the number of ways to arrange the numbers 1 to n so that a and a+1 (or n and 1) will never occur in positions b and b+1 (or n and 1.)
For n=2, there are none. (This makes it clear that f(2) = 0.
For n=3, we have 2,1,3; 1,3,2; and 3,2,1. So f(3) must be 3.
For n=4, we have:
So f(4) must be 4.
For n=5, there's:
This means f(5) must be 35.
Anyone know the sequence to at least f(11)?? Georgia guy ( talk) 19:06, 20 June 2021 (UTC)
Mathematics desk | ||
---|---|---|
< June 19 | << May | June | Jul >> | June 21 > |
Welcome to the Wikipedia Mathematics Reference Desk Archives |
---|
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
Can anyone find the sequence with this rule:
Find the number of ways to arrange the numbers 1 to n so that a and a+1 (or n and 1) will never occur in positions b and b+1 (or n and 1.)
For n=2, there are none. (This makes it clear that f(2) = 0.
For n=3, we have 2,1,3; 1,3,2; and 3,2,1. So f(3) must be 3.
For n=4, we have:
So f(4) must be 4.
For n=5, there's:
This means f(5) must be 35.
Anyone know the sequence to at least f(11)?? Georgia guy ( talk) 19:06, 20 June 2021 (UTC)