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A349456
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Number of singular positroid varieties corresponding to derangements in S_n.
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3
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OFFSET
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0,5
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COMMENTS
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a(n) is also the number of derangements whose chordal diagrams have crossed alignments.
a(n) counts the complement of A349413 in the set of all derangements of S_n (A000166).
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LINKS
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FORMULA
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EXAMPLE
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For n=4 the a(4)=4 derangements in one-line notation corresponding to singular positroid varieties are 2413, 3421, 3142, and 4312.
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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