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

Author

Cheyne Homberger, Oct 23 2013

Keywords

• nonn

Examples

			Of the 26 involutions of length 5, only 14523 and 15342 contain the pattern 1342, so a(5) = 24.
		

Links

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

Crossrefs

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