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A263778 Number of inversion sequences avoiding pattern 120. 27
1, 1, 2, 6, 23, 103, 515, 2803, 16334, 100700, 650905, 4380595, 30528410, 219352058, 1619260140, 12245357074, 94636062782, 745907086918, 5985448211508, 48824435255942, 404330087326924, 3395418226577756, 28884708430087203, 248696210256230427 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Number of length n inversion sequences avoiding e_k < e_i < e_j for i<j<k. A length n inversion sequence e_1,e_2,...,e_n consists of nonnegative integers e_t <= t-1. - Alois P. Heinz, Dec 20 2016

LINKS

Table of n, a(n) for n=0..23.

Sylvie Corteel, Megan A. Martinez, Carla D. Savage, Michael Weselcouch, Patterns in Inversion Sequences I, arXiv:1510.05434 [math.CO], 2015.

Megan A. Martinez, Carla D. Savage, Patterns in Inversion Sequences II: Inversion Sequences Avoiding Triples of Relations, arXiv:1609.08106 [math.CO], 2016.

CROSSREFS

Cf. A263777, A263779, A263780.

Sequence in context: A216040 A005802 A061552 * A053488 A117106 A137534

Adjacent sequences:  A263775 A263776 A263777 * A263779 A263780 A263781

KEYWORD

nonn

AUTHOR

Michel Marcus, Oct 26 2015

EXTENSIONS

a(0)=1 prepended by Alois P. Heinz, Dec 15 2016

a(10)-a(23) from Alois P. Heinz, Dec 20 2016

STATUS

approved

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Last modified February 18 02:57 EST 2020. Contains 332006 sequences. (Running on oeis4.)