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A351159
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Number of polyominoes of n cells with both diagonal symmetries, for which the 180-degree rotational symmetry has an axis that coincides with the center of a square, but without 90-degree rotational symmetry.
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2
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0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 2, 1, 3, 1, 6, 4, 9, 6, 20, 19, 32, 25, 64, 82, 114, 107, 217, 332, 397, 442, 751, 1316
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OFFSET
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1,11
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COMMENTS
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This sequence enumerates a subset of the polyominoes enumerated by A056878.
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LINKS
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FORMULA
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EXAMPLE
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For a(7)=1, the heptomino with exactly fourfold symmetry and axes of symmetry parallel to the diagonals of the cells is composed of two 2 X 2 squares with one cell in common.
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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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STATUS
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approved
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