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A287220
Number of single-crossing partitions on n nodes.
3
0, 0, 1, 4, 10, 36, 85, 312, 737, 2760, 6604, 25176
OFFSET
0,4
COMMENTS
The meandric numbers A005316 are the numbers of paths which cross themselves 0 times.
This sequence is the number of paths that must cross themselves exactly once.
EXAMPLE
a(2) = 1, this is from the partition (2,1).
a(3) = 4, this is from the partitions (1,3,2),(2,1,3),(2,3,1),(3,1,2).
CROSSREFS
Sequence in context: A222506 A108596 A204270 * A220205 A196880 A359688
KEYWORD
nonn,more
AUTHOR
STATUS
approved