A260694 Number of up-down parking functions of length n.

1, 1, 1, 4, 17, 120, 915, 9470, 104436, 1432713, 20709209, 354493902, 6343919118, 130255212146, 2780356513594, 66607482974307, 1651884203936474, 45240390673466869, 1278413274487999471, 39403978336643657797, 1249821733374560346851, 42820844948653526713511

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: A335945 A360879 A206353 * A032115 A054927 A307794

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