A230553 Number of involutions avoiding the pattern 1342.

1, 1, 2, 4, 10, 24, 62, 156, 406, 1040, 2714, 7012, 18322, 47560, 124358, 323708, 846766, 2208032, 5777330, 15082372, 39469786

Offset

0,3

Links

Table of n, a(n) for n=0..20.

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 14523 and 15342 contain the pattern 1342, so a(5) = 24.

Crossrefs

Cf. A000085, A001006, A121704, A230551-A230556.

Sequence in context: A307900 A230551 A246566 * A138175 A121691 A124499

Adjacent sequences: A230550 A230551 A230552 * A230554 A230555 A230556

Keyword

nonn

Author

Cheyne Homberger, Oct 23 2013

Status

approved