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A122647 Number of permutations of length 2n-1 with no local maxima or minima in even positions. 1
1, 2, 14, 204, 5104, 195040, 10570416, 771171296, 72871890176, 8658173200896, 1263326817241600, 222078432102900736, 46291130226003357696, 11289508838355990634496, 3184719803676823556888576, 1028950134725811309304442880, 377483869192551997938994315264, 156057810922284533544621710639104 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..18.

Guo-Niu Han, Enumeration of Standard Puzzles

Guo-Niu Han, Enumeration of Standard Puzzles [Cached copy]

M. La Croix, A combinatorial proof of a result of Gessel and Greene, Discr. Math., 306 (2006), 2251-2256.

FORMULA

a(n) = A113583(n)/2^(n-1).

CROSSREFS

CF. A113583.

Sequence in context: A279452 A262008 A054652 * A158097 A262003 A271847

Adjacent sequences:  A122644 A122645 A122646 * A122648 A122649 A122650

KEYWORD

nonn,changed

AUTHOR

N. J. A. Sloane, Sep 21 2006

STATUS

approved

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Last modified January 25 03:49 EST 2020. Contains 331241 sequences. (Running on oeis4.)