A308750 Number of Dumont permutations of the first kind of length 2n avoiding pattern 2143 (or pattern 3421).

1, 1, 2, 7, 36, 239, 1892, 17015, 168503, 1799272, 20409644

Offset

0,3

Comments

Conjecture: The number of Dumont permutations of the first kind avoiding pattern 2143 equals the number of Dumont permutations of the first kind avoiding pattern 3421 for all n >= 0.

Data for n=7,8,9,10 is due to Michael Albert.

References

O. Jones, Enumeration of Dumont permutations avoiding certain four-letter patterns, Ph.D. thesis, Howard University, 2019.

Links

Table of n, a(n) for n=0..10.

D. Dumont, Interprétations combinatoires des nombres de Genocchi, Duke Math. J., 41 (1974), 305-318.

Example

For n=3, the 7 Dumont permutations of the first kind avoiding pattern 2143 are 356421, 364215, 435621, 563421, 564213, 634215, 642135, and the 7 Dumont permutations of the first kind avoiding pattern 3421 are 214365, 216435, 421365, 421563, 421635, 621435, 642135.

Crossrefs

Cf. A001469, A110501.

Sequence in context: A212411 A119736 A353166 * A088715 A088313 A201197

Adjacent sequences: A308747 A308748 A308749 * A308751 A308752 A308753

Keyword

nonn,more

Author

Alexander Burstein and Opel Jones, Jun 21 2019

Status

approved