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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
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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.
LINKS
Table of n, a(n) for n=0..11.
B. W. J. Irwin,
On the number of k-crossing partitions
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
Cf.
A005316
,
A287221
.
Sequence in context:
A222506
A108596
A204270
*
A220205
A196880
A359688
Adjacent sequences:
A287217
A287218
A287219
*
A287221
A287222
A287223
KEYWORD
nonn
,
more
AUTHOR
Benedict W. J. Irwin
, May 22 2017
STATUS
approved
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Last modified May 7 09:38 EDT 2024. Contains 372302 sequences. (Running on oeis4.)