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Topic: Re: How many concave quadrilaterals are in a 3 by n array?
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luechtdiode

Posts: 2
Registered: 1/26/14
Re: How many concave quadrilaterals are in a 3 by n array?
Posted: Jan 26, 2014 9:38 PM
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The formula works perfectly and it prevents me from brute-forcing:
For odd n use P(n) = (11n^4 - 30n^3 + 16n^2 -18n +21)/8.
For even n use P(n) = (11n^4 - 30n^3 + 16n^2)/8.

But I cannot understand why. For example, I would use this approach with a n x m -grid. Where are the m-parts in that formula (should be constant 3)?

Are there any hints to the basics of the mentioned approach?



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