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

Author

Cheyne Homberger, Oct 23 2013

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Cf. A001006, A121704, A230551-A230556.