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Magic circle revisited (Posted on 2017-12-22) Difficulty: 3 of 5
Here are counters numbered 0-9 in a circle:

        1                   2

  8                               7

  4                               5

        6                   3

The property that makes it a magic circle is: there is a specific starting counter (in this case the 9) so that if you proceed clockwise by that number of steps and repeat the process with each new number you eventually visit every number and end at zero.

Given numbers 0-n:
For what values of n does a magic circle exist?
For a given value of n, how many magic circles exist?
Are there infinite families of magic circles?

No Solution Yet Submitted by Jer    
Rating: 3.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
A trivial exception | Comment 3 of 5 |
I have proved that n must be odd (see earlier post), because otherwise the starting counter would need to be on the space occupied by zero.

However, arguably, n = 0 is a trivial magic circle.  In this case, there is only one number, zero, and it is both the starting and ending counter.

So the answer to the first question is "any positive odd n, plus n = 0"

  Posted by Steve Herman on 2017-12-23 13:00:14
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