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Search: id:A134648
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| A134648 |
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Number of m X n (0,1)-matrices with every row sum 4 and column sum 2. |
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+0
1
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OFFSET
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2,2
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FORMULA
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a(m,n) = 24^{-m} Sum_{alpha = 0 ..m} Sum_{beta = 0 .. m-alpha } \frac{% (-1)^{(m-alpha -beta )}3^{alpha }6^{(m-alpha -beta )}m!n!(4beta +2(m-alpha -beta ))!}{alpha !beta !(m-alpha -beta )!(2beta +(m-alpha-beta ))!2^{2beta +(m-alpha -beta )}}
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CROSSREFS
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Adjacent sequences: A134645 A134646 A134647 this_sequence A134649 A134650 A134651
Sequence in context: A112004 A116273 A036257 this_sequence A052277 A066784 A135321
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KEYWORD
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nonn,uned
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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+2 (0,1)-matrices ..." ? - njas. Also what is the symbol "%" in the formula?
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