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A279558 Number of length n inversion sequences avoiding the patterns 010, 120, and 210. 22
1, 1, 2, 5, 15, 52, 200, 830, 3654, 16869, 80963, 401300, 2043610, 10649335, 56604706, 306101789, 1680515427 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
COMMENTS
A length n inversion sequence e_1e_2...e_n is a sequence of integers where 0 <= e_i <= i-1. The term a(n) counts those length n inversion sequences with no entries e_i, e_j, e_k (where i<j<k) such that e_i <> e_j > e_k and e_i >= e_k. This is the same as the set of length n inversion sequences avoiding 010, 120, and 210.
LINKS
Megan A. Martinez, Carla D. Savage, Patterns in Inversion Sequences II: Inversion Sequences Avoiding Triples of Relations, arXiv:1609.08106 [math.CO], 2016-2018.
EXAMPLE
The length 4 inversion sequences avoiding (010, 120, 210) are 0000, 0001, 0002, 0003, 0011, 0012, 0013, 0021, 0022, 0023, 0111, 0112, 0113, 0122, 0123.
CROSSREFS
Sequence in context: A370798 A007312 A007296 * A224071 A202062 A279559
KEYWORD
nonn,more
AUTHOR
Megan A. Martinez, Jan 17 2017
EXTENSIONS
a(10)-a(12) from Alois P. Heinz, Feb 24 2017
a(13)-a(16) from Bert Dobbelaere, Dec 30 2018
STATUS
approved

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Last modified July 18 13:57 EDT 2024. Contains 374378 sequences. (Running on oeis4.)