Let be an integer. Each face of a regular tetrahedron is painted in one of colors (the faces are not necessarily painted different colors.) Suppose there are possible colorings, where rotations, but not reflections, of the same coloring are considered the same. Find all possible values of .
Solution
We count the possible number of colorings. If four colors are used, there are two different colorings that are mirror images of each other, for a total of colorings. If three colors are used, we choose one color to use twice (which determines the coloring), for a total of colorings. If two colors are used, we can either choose one of those colors and color three faces with it, or we can color two faces each color, for a total of colorings. Finally, we can also use only one color, for colorings. This gives a total of colorings. Setting this equal to , we get the equation , or equivalently , giving the answers 1 and 11.
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