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I would appreciate a hint for puzzle 23. I am struggling to derive a recurrence relation or formula. How to find the pattern for number of ways?
Reza
on /blog/107
×1   ×1   ×1   ×1   ×1   
@Reza:

I didn't use a recurrence. When dividing into three areas, one of the the lines must span the entire grid creating two areas. Then one more line is used to split one of the just created areas into three areas. I just figured out how many ways there are to place the first line, then how many ways there are to place the second. There are two main scenarios you need to deal with:
1) Two horizontal or vertical lines
2) One horizontal and one vertical line

Hope that helps
Aaron
on /blog/107
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@Aaron: Wow thank you Aaron, that was just the idea I needed. Very fun.
Reza
on /blog/107
×3   ×3   ×3   ×3   ×3   

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