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So I have the following task:

We have a rectangle $2 \times 4$ cells and four colors: red, green, blue, black. How many ways are there to paint each cell, so that no two cells with a common side were painted the same color.

How to solve this? I'm interested in the explanation first and some pattern for such tasks cause my teacher didn't explain me.

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    You may also see this one: http://math.stackexchange.com/questions/112565/coloring-a-4-times-4-square-with-4-colors , which is a harder problem!2012-05-14

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