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 A279555 Number of length n inversion sequences avoiding the patterns 110, 210, 120, and 010. 22
 1, 1, 2, 5, 15, 51, 189, 746, 3091, 13311, 59146, 269701, 1256820, 5966001, 28773252, 140695923, 696332678, 3483193924, 17589239130, 89575160517, 459648885327, 2374883298183, 12346911196912, 64555427595970, 339276669116222, 1791578092326881, 9501960180835998 (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 e_k and e_i >= e_k. This is the same as the set of length n inversion sequences avoiding 010, 110, 120, and 210. It can be shown that this sequence also counts the length n inversion sequences with no entries e_i, e_j, e_k (where i e_j >=e_k and e_i >= e_k. This is the same as the set of length n inversion sequences avoiding 010, 100, 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. EXAMPLE The length 3 inversion sequences avoiding (010, 110, 120, 210) are 000, 001, 002, 011, 012. The length 4 inversion sequences avoiding (010, 110, 120, 210) are 0000, 0001, 0002, 0003, 0011, 0012, 0013, 0021, 0022, 0023, 0111, 0112, 0113, 0122, 0123. CROSSREFS Cf. A263777, A263778, A263779, A263780, A279551, A279552, A279553, A279554, A279556, A279557, A279558, A279559, A279560, A279561, A279562, A279563, A279564, A279565, A279566, A279567, A279568, A279569, A279570, A279571, A279572, A279573. Sequence in context: A007317 A181768 A279554 * A153197 A299968 A279556 Adjacent sequences:  A279552 A279553 A279554 * A279556 A279557 A279558 KEYWORD nonn AUTHOR Megan A. Martinez, Dec 16 2016 EXTENSIONS a(10)-a(26) from Alois P. Heinz, Jan 05 2017 STATUS approved

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Last modified January 22 07:39 EST 2020. Contains 331139 sequences. (Running on oeis4.)