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A035482
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Number of n X n symmetric matrices each of whose rows is a permutation of 1..n.
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1
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OFFSET
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0,3
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COMMENTS
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The even and odd subsequences are A036980, A036981.
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LINKS
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Table of n, a(n) for n=0..9.
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FORMULA
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a(n) = A035481(n) * n!. [From Max Alekseyev, Apr 23 2010]
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EXAMPLE
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a(3) = 6 because the first row is arbitrary (say, 213) and the rest is then determined. By symmetry the second row has to be 132 or 123 but in order for the third row/column to work it has to be 132.
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CROSSREFS
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Cf. A000438, A035481, A000315, A002860, A003090, A040082.
Sequence in context: A280117 A129364 A092287 * A322716 A007870 A081992
Adjacent sequences: A035479 A035480 A035481 * A035483 A035484 A035485
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KEYWORD
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more,nonn
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AUTHOR
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Joshua Zucker and Joe Keane
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STATUS
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approved
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