A287222 Number of 3-time self-crossing partitions on n nodes.

0, 0, 0, 0, 2, 16, 164, 944, 4386, 22240, 83066, 398132

Offset

0,5

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 3 times.

Links

Table of n, a(n) for n=0..11.

B. W. J. Irwin, On the number of k-crossing partitions

Example

a(4) = 2, this is from the partitions (2,4,1,3) and (3,4,1,2).

Crossrefs

Cf. A005316, A287220, A287221.

Sequence in context: A011552 A374848 A326362 * A216598 A219397 A275912

Adjacent sequences: A287219 A287220 A287221 * A287223 A287224 A287225

Keyword

nonn,more

Author

Benedict W. J. Irwin, May 22 2017

Status

approved