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

Author

Alexander Burstein and Opel Jones, Jun 21 2019

Keywords

• nonn
• more

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.

Examples

			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.
		

References

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

Links

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

Crossrefs

Cf. A001469, A110501.