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A359519
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Number of free polyominoes of n cells with multiply-connected interiors.
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2
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0, 0, 0, 0, 0, 0, 0, 1, 2, 16, 70, 378, 1772, 8456, 38623, 174400, 771944, 3378937
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OFFSET
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1,9
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LINKS
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FORMULA
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a(n) = A000105(n) - A342537(n) (all free polyominoes minus simply-connected interior polyominoes).
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EXAMPLE
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a(8) = 1 because of:
OOO
O O
OOO
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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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