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A193774
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Number of signed permutations of length n invariant under the reverse complement and avoiding (-2, 1) and (2, -1).
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0
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1, 2, 4, 6, 20, 26, 124, 146, 956, 1050, 9100
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OFFSET
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0,2
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LINKS
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Table of n, a(n) for n=0..10.
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EXAMPLE
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For n = 2, the permutations are (1, 2), (2, 1), (-1, -2), and (-2, -1).
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CROSSREFS
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Sequence in context: A279188 A108439 A245766 * A241210 A333992 A176652
Adjacent sequences: A193771 A193772 A193773 * A193775 A193776 A193777
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KEYWORD
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nonn
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AUTHOR
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Andy Hardt, Aug 04 2011
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STATUS
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approved
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