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A013498 Number of permutations in S_n with a certain property. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
LINKS
Frank Schmidt and Rodica Simion, Card shuffling and a transformation on S_n, Aequationes Math. 44 (1992), no. 1, 11-34.
MAPLE
binomial(n-2, floor(n/2)-1) + floor((n-1)/2)*binomial(n-3, floor(n/2)-2);
CROSSREFS
Sequence in context: A191391 A121482 A368858 * A161624 A247794 A034758
KEYWORD
nonn,easy
AUTHOR
STATUS
approved

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Last modified April 12 06:13 EDT 2024. Contains 371623 sequences. (Running on oeis4.)