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A308750 Number of Dumont permutations of the first kind of length 2n avoiding pattern 2143 (or pattern 3421). 0
1, 1, 2, 7, 36, 239, 1892, 17015, 168503, 1799272, 20409644 (list; graph; refs; listen; history; text; internal format)
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, Interpr├ętations 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: A019030 A212411 A119736 * 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

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Last modified May 27 02:42 EDT 2020. Contains 334647 sequences. (Running on oeis4.)