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Search: id:A134645
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| A134645 |
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Number of m X n (-1,0,1)-matrices with every row sum 3 and column sum 2. |
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+0
2
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| 7, 16260, 747558000, 250071339672000, 369820640830881240000
(list; graph; listen)
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OFFSET
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2,1
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REFERENCES
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Zhonghua Tan and Shanzhen Gao,Counting (0,1,2)- Matrices, submitted
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FORMULA
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t(m,n)=6^{-m} sum_{i=0}^{m}frac{3^{i}m!n!(2n-2i)!}{% i!(m-i)!(n-i)!2^{n-i}}
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CROSSREFS
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Cf. A000681.
Adjacent sequences: A134642 A134643 A134644 this_sequence A134646 A134647 A134648
Sequence in context: A067248 A152007 A131676 this_sequence A115997 A013786 A072050
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KEYWORD
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nonn
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AUTHOR
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Shanzhen Gao (sgao2(AT)fau.edu), Nov 05 2007
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EXTENSIONS
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Perhaps "Number of n X n+1 (-1,0,1)-matrices ..." ? - njas
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