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Search: id:A086899
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| A086899 |
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Number of real n X n invertible symmetric (0,1) matrices. |
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+0
6
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OFFSET
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1,2
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LINKS
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Index entries for sequences related to binary matrices
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EXAMPLE
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For n = 2 the 4 matrices are 10/01, 01/10, 11/10, 01/11.
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MATHEMATICA
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triamat[li_List] := (*see A086900*); Table[it=triamat/@IntegerDigits[Range[0, -1+2^(n(n+1)/2)], 2, n(n+1)/2]; Count[it, (q_)?MatrixQ/; (Det[q]=!=0)], {n, 5}]
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CROSSREFS
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Cf. A086900, A086906, A118991.
Sequence in context: A118990 A036442 A127945 this_sequence A012509 A013041 A006024
Adjacent sequences: A086896 A086897 A086898 this_sequence A086900 A086901 A086902
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KEYWORD
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nonn,more
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AUTHOR
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Wouter Meeussen (wouter.meeussen(AT)pandora.be) Aug 23, 2003.
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EXTENSIONS
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a(6) and a(7) from Giovanni Resta (g.resta(AT)iit.cnr.it), May 08 2006
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