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A230554
Number of involutions avoiding the pattern 1324.
5
1, 1, 2, 4, 9, 21, 51, 126, 321, 820, 2160, 5654, 15272, 40758, 112280, 304471, 852164, 2341980, 6640755, 18460066, 52915999
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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 [math.CO], 2013-2014.
EXAMPLE
Of the 26 involutions of length 5, only 21435, 13254, 13245, 14325, and 12435 contain the pattern 1324, so a(5) = 21.
CROSSREFS
Cf. A000085, A001006, A121704, A230551, A230552, A230553, A230555, A230556.
Sequence in context: A257386 A048285 A051529 * A005207 A257519 A257387
Adjacent sequences: A230551 A230552 A230553 * A230555 A230556 A230557
KEYWORD
nonn,more
AUTHOR
Cheyne Homberger, Oct 23 2013
STATUS
approved

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Last modified May 22 02:26 EDT 2026. Contains 395813 sequences.
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