A129815 Number of reverse alternating fixed-point-free permutations on n letters.

0, 0, 1, 2, 6, 22, 102, 506, 2952, 18502, 131112, 991226, 8271792, 73176262, 703077552, 7121578106, 77437418112, 883521487942, 10726837356672, 136104948161786, 1825110309733632

Offset: 1

Author

Vladeta Jovovic, May 20 2007

Keywords

• more
• nonn

Comments

From Emeric Deutsch, Aug 06 2009: (Start)

Reverse alternating permutations are called also up-down permutations.

a(n) is also the number of reverse alternating permutations having exactly 1 fixed point (see the Stanley reference). Example: a(4)=2 because we have 1423 and 2314.

(End)

Examples

			a(4)=2 because we have 3412 and 2413. [_Emeric Deutsch_, Aug 06 2009]
		

Links

• R. P. Stanley, Alternating permutations and symmetric functions, arXiv:math/0603520 [math.CO], 2006.

Crossrefs

Cf. A000111, A000166, A007779, A129817.

Formula

a(2n-1) = A129817(2n-1). [Emeric Deutsch, Aug 06 2009]

Extensions

a(21) from Alois P. Heinz, Jun 11 2015