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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

Table of n, a(n) for n=1..31.

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: A177143 A191391 A121482 * A161624 A247794 A034758

Adjacent sequences: A013495 A013496 A013497 * A013499 A013500 A013501

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified January 29 00:02 EST 2023. Contains 359905 sequences. (Running on oeis4.)