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Search: id:A013498
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| A013498 |
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Number of permutations in S_n with a certain property. |
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+0
1
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| 1, 0, 1, 3, 5, 12, 22, 50, 95, 210, 406, 882, 1722, 3696, 7260, 15444, 30459, 64350, 127270, 267410, 529958, 1108536, 2200276, 4585308, 9111830, 18929092, 37650172, 78004500, 155266100, 320932800, 639191160
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OFFSET
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1,4
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REFERENCES
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Frank Schmidt and Rodica Simion, Card shuffling and a transformation on S_n, Aequationes Math. 44 (1992), no. 1, 11-34.
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MAPLE
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binomial(n-2, floor(n/2)-1) + floor((n-1)/2)*binomial(n-3, floor(n/2)-2);
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CROSSREFS
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Sequence in context: A089292 A034763 A121482 this_sequence A034758 A131322 A036657
Adjacent sequences: A013495 A013496 A013497 this_sequence A013499 A013500 A013501
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KEYWORD
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nonn,easy
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AUTHOR
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njas
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