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Search: id:A129817
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| A129817 |
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Number of alternating fixed-point-free permutations on n letters. |
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+0
2
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| 0, 1, 1, 2, 6, 24, 102, 528, 2952, 19008, 131112, 1009728, 8271792, 74167488, 703077552, 7194754368, 77437418112, 890643066048, 10726837356672, 136988469649728
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OFFSET
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1,4
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COMMENT
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For n>0 a(2n-1)=A129815(2n-1); for n>1 a(2n)=A129815(2n)+ A129815(2n-2). - Vladimir Shevelev (shevelev(AT)bgu.ac.il), Apr 29 2008
We conjecture that for n>=3, A000111(2n)/a(2n) < e < A000111(2n)/A129815(2n), so that A000111(2n)/a(2n) increases while A000111(2n)/A129815(2n) decreases (and both quotients tend to e) - Vladimir Shevelev (shevelev(AT)bgu.ac.il), Apr 29 2008
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LINKS
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R. P. Stanley, Alternating permutations and symmetric functions
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CROSSREFS
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Cf. A000111, A000166, A007779.
Sequence in context: A094012 A141253 A078486 this_sequence A128652 A094433 A141254
Adjacent sequences: A129814 A129815 A129816 this_sequence A129818 A129819 A129820
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KEYWORD
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more,nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu), May 20 2007
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