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A230552 Number of involutions avoiding the pattern 2341. 1
1, 2, 4, 10, 25, 66, 170, 441, 1124, 2870, 7273, 18477, 46825, 118917, 301734, 766525, 1946293, 4944614, 12557685 (list; graph; refs; listen; history; text; internal format)
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

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Last modified June 24 06:17 EDT 2021. Contains 345416 sequences. (Running on oeis4.)