cp's OEIS Frontend

A279572 Number of length n inversion sequences avoiding the patterns 120, 201, and 210.

%I A279572 #21 Jan 20 2024 11:10:24
%S A279572 1,1,2,6,23,101,484,2468,13166,72630,411076,2374188,13938018,82932254,
%T A279572 499031324,3031610924,18568429963,114541486785,710973143614,
%U A279572 4437415155234,27831038618735,175318861863701,1108762012137252,7037137177329268,44808588430903068
%N A279572 Number of length n inversion sequences avoiding the patterns 120, 201, and 210.
%C A279572 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, 201, and 210.
%H A279572 Toufik Mansour, Howard Skogman, and Rebecca Smith, <a href="https://arxiv.org/abs/2401.06662">Sorting inversion sequences</a>, arXiv:2401.06662 [math.CO], 2024. See Theorem 4.3 at page 16.
%H A279572 Megan A. Martinez and 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], 2016-2018.
%e A279572 The length 4 inversion sequences avoiding (120, 201, 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 A279572 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, A279573.
%K A279572 nonn
%O A279572 0,3
%A A279572 _Megan A. Martinez_, Feb 21 2017
%E A279572 a(12)-a(15) from _Bert Dobbelaere_, Dec 30 2018
%E A279572 a(16)-a(24) from _Toufik Mansour_ et al. added by _Stefano Spezia_, Jan 20 2024