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A288027
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Number of minimal edge covers in the grid graph P_n X P_n.
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3
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OFFSET
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1,2
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COMMENTS
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A minimal edge cover is an edge cover such that the removal of any edge in the cover destroys the covering property. Equivalently, these are the edge covers whose connected components are stars.
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LINKS
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EXAMPLE
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In the 3 X 3 grid, the minimal edge covers up to rotation and reflection are:
.__.__. .__.__. .__.__. .__.__. .__.__. .__. .
.__.__. . . . .__. . . .__. . | . . | |
.__.__. | | | .__. | |__. | | .__| | .__.
The first two of these need to be counted 2 and 4 times and the rest which have no symmetry 8 times so a(3) = 38.
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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