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Search: id:A126742
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| A126742 |
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Number of n-indecomposable polyominoes with at least 2n cells. |
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+0
6
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OFFSET
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1,2
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COMMENT
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A polyomino is called n-indecomposable if it cannot be partitioned (along cell boundaries) into two or more polyominoes each with at least n cells.
For full lists of drawings of these polyominoes for n <= 6, see the links in A125759.
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REFERENCES
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N. MacKinnon, Some thoughts on polyomino tilings, Math. Gaz., 74 (1990), 31-33.
S. Rinaldi and D. G. Rogers, Indecomposability: polyominoes and polyomino tilings, Math. Gaz., to appear, 2008.
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EXAMPLE
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The five 2-indecomposable polyominoes:
...................X.
XX..XXX..XX..XXX..XXX
..........X...X....X.
Only the last two have >= 4 cells, so a(2) = 2.
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CROSSREFS
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Row sums of A126743. Cf. A000105, A125759, A125761, A125709, A125753.
Sequence in context: A134296 A086510 A123113 this_sequence A013051 A012955 A011808
Adjacent sequences: A126739 A126740 A126741 this_sequence A126743 A126744 A126745
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KEYWORD
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nonn,more
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AUTHOR
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David Applegate (david(AT)research.att.com) and njas, Feb 01 2007
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EXTENSIONS
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a(4) and a(5) from Peter Pleasants, Feb 13 2007
a(6) and a(7) from David Applegate (david(AT)research.att.com), Feb 16 2007
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