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Search: id:A035481
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| A035481 |
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Number of n X n symmetric matrices whose first row is 1..n and whose rows and columns are all permutations of 1..n. |
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+0
7
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OFFSET
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0,5
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COMMENT
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The odd subsequence is presumably A000438, which gives more terms. The even subsequence is A035483.
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EXAMPLE
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a(3) = 1 because after 123 in the first row and column, 213 is not allowed for the second row, so it must be 231, and thus the third row is 312.
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CROSSREFS
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Cf. A000438, A035482, A000315, A002860, A003090, A040082.
Sequence in context: A113838 A056831 A027717 this_sequence A061214 A137024 A054264
Adjacent sequences: A035478 A035479 A035480 this_sequence A035482 A035483 A035484
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KEYWORD
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more,nonn,nice
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AUTHOR
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Joshua Zucker and Joe Keane (joshua.zucker(AT)stanfordalumni.org)
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