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3 in a row = bad (Posted on 2006-04-26) Difficulty: 4 of 5
For n=3,4,5,6,7,8 find:

a) The minimum number of counters that need be placed on a nxn chessboard such that no additional counters can be placed without creating any straight line of 3;

b) The maximum number of counters that can be placed on a nxn chessboard such that no three lie in a straight line.

Remember that positions like A1, B3, and C5 are in a straight line.
(Try to continue the sequences if you can)

See The Solution Submitted by Jer    
Rating: 4.5000 (2 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Some Thoughts re: Possible minimum? | Comment 4 of 13 |
(In reply to Possible minimum? by tomarken)

Turns out that for a 7x7 grid, part (a) can be accomplished with only 10 markers.  Still don't know if that's the minimum, although I suspect that it is.  I haven't checked to see if there are better solutions for the others yet...
  Posted by tomarken on 2006-04-26 16:43:35

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