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 A279573 Number of length n inversion sequences avoiding the patterns 120 and 210. 23

%I

%S 1,1,2,6,23,102,499,2625,14601,84847,510614,3161964,20050770,

%T 129718404,853689031,5701759424,38574689104,263936457042,

%U 1824032887177,12718193293888,89386742081688,632746535420834,4508140253686638,32308561883462867,232790342330880572

%N Number of length n inversion sequences avoiding the patterns 120 and 210.

%C 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 120 and 210.

%H Alois P. Heinz, <a href="/A279573/b279573.txt">Table of n, a(n) for n = 0..400</a>

%H Megan A. Martinez, Carla D. Savage, <a href="https://arxiv.org/abs/1609.08106">Patterns in Inversion Sequences II: Inversion Sequences Avoiding Triples of Relations</a>, arXiv:1609.08106 [math.CO], 2016.

%H Chunyan Yan, Zhicong Lin, <a href="https://arxiv.org/abs/1912.03674">Inversion sequences avoiding pairs of patterns</a>, arXiv:1912.03674 [math.CO], 2019.

%e The length 4 inversion sequences avoiding (120,210) are 0000, 0001, 0002, 0003, 0010, 0011, 0012, 0013, 0020, 0021, 0022, 0023, 0100, 0101, 0102, 0103, 0110, 0111, 0112, 0113, 0121, 0122, 0123.

%Y Cf. A000108, A057552, A263777, A263778, A263779, A263780, A279551, A279552, A279553, A279554, A279555, A279556, A279557, A279558, A279559, A279560, A279561, A279562, A279563, A279564, A279565, A279566, A279567, A279568, A279569, A279570, A279571, A279572.

%K nonn

%O 0,3

%A _Megan A. Martinez_, Feb 21 2017

%E a(10)-a(24) from _Alois P. Heinz_, Feb 21 2017

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Last modified March 29 03:09 EDT 2020. Contains 333104 sequences. (Running on oeis4.)