A230552 Number of involutions avoiding the pattern 2341.

1, 2, 4, 10, 25, 66, 170, 441, 1124, 2870, 7273, 18477, 46825, 118917, 301734, 766525, 1946293, 4944614, 12557685

Offset

1,2

Links

Table of n, a(n) for n=1..19.

Miklós Bóna, Cheyne Homberger, Jay Pantone, and Vince Vatter, Pattern-avoiding involutions: exact and asymptotic enumeration, arxiv:1310.7003, 2013.

Example

Of the 26 involutions of length 5, only 52341 contains the pattern 2341, so a(5) = 25.

Crossrefs

Cf. A001006, A121704, A230551-A230556.

Sequence in context: A000645 A005958 A166516 * A230555 A189912 A268321

Adjacent sequences: A230549 A230550 A230551 * A230553 A230554 A230555

Keyword

nonn

Author

Cheyne Homberger, Oct 23 2013

Status

approved