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A260694 Number of up-down parking functions of length n. 1
1, 1, 1, 4, 17, 120, 915, 9470, 104436, 1432713, 20709209, 354493902, 6343919118, 130255212146, 2780356513594, 66607482974307, 1651884203936474, 45240390673466869, 1278413274487999471, 39403978336643657797, 1249821733374560346851, 42820844948653526713511 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

A parking function (c_1, c_2, c_3, c_4, c_5 ..., c_n) is up-down if c_1 < c_2 > c_3 < c_4 > c_5... .

Clearly, A000111(n) <= a(n) <= A000272(n+1).

LINKS

Table of n, a(n) for n=0..21.

FORMULA

a(2n) = A264963(2n). - Alois P. Heinz, Nov 29 2015

EXAMPLE

For n = 3, the a(3) = 4 up-down parking functions are (1,3,1), (1,2,1), (1,3,2), (2,3,1).

CROSSREFS

Cf. A000111, A000272, A264963.

Sequence in context: A271612 A240323 A206353 * A032115 A054927 A071138

Adjacent sequences:  A260691 A260692 A260693 * A260695 A260696 A260697

KEYWORD

nonn

AUTHOR

Ran Pan, Nov 16 2015

EXTENSIONS

a(0),a(10)-a(21) from Alois P. Heinz, Nov 25 2015, Nov 29 2015

STATUS

approved

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Last modified September 26 06:54 EDT 2017. Contains 292502 sequences.