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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
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
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
Sequence in context: A212411 A119736 A353166 * A088715 A373773 A088313
KEYWORD
nonn,more
AUTHOR
STATUS
approved