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A209230 Number of set partitions of [n] that avoid 1231 and 1121. 0
1, 1, 2, 5, 13, 34, 88, 226, 578, 1476, 3768, 9620, 24564, 62728, 160192, 409096, 1044744, 2668048, 6813600, 17400400, 44436688, 113481248, 289805440, 740097568, 1890041888, 4826739776, 12326402432 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
LINKS
V. Jelinek, T. Mansour, M. Shattuck, On multiple pattern avoiding set partitions, Adv. Appl. Math. 50 (2) (2013) 292-326, Example 4.16 H_{1121} and example 4.17 L_{1121}.
FORMULA
G.f (1-x-x^2)*(1-x)^2/(1-4*x+4*x^2-2*x^4), correcting a sign in denominators of the publication.
CROSSREFS
Sequence in context: A027931 A218481 A267905 * A103142 A112844 A027933
KEYWORD
nonn,easy
AUTHOR
R. J. Mathar, Jan 12 2013
STATUS
approved

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Last modified February 25 10:04 EST 2024. Contains 370314 sequences. (Running on oeis4.)