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A279552 Number of length n inversion sequences avoiding the patterns 000 and 010. 22
1, 1, 2, 4, 10, 29, 95, 345, 1376, 5966, 27886, 139608, 744552, 4210191, 25140790, 157981820, 1041480482, 7183374125, 51711299169, 387683162541, 3020997261596 (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_j >= e_k and e_i = e_k. This is the same as the set of length n inversion sequences avoiding 000 and 010.

LINKS

Table of n, a(n) for n=0..20.

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

EXAMPLE

For n=3, the inversion sequences are 001, 002, 011, 012.

For n=4, the inversion sequences are 0011, 0012, 0013, 0021, 0022, 0023, 0112, 0113, 0122, 0123.

CROSSREFS

Cf. A263777, A263778, A263779, A263780, A279551, A279553, A279554, A279555, A279556, A279557, A279558, A279559, A279560, A279561, A279562, A279563, A279564, A279565, A279566, A279567, A279568, A279569, A279570, A279571, A279572, A279573.

Sequence in context: A086631 A320903 A230957 * A261041 A047051 A271077

Adjacent sequences:  A279549 A279550 A279551 * A279553 A279554 A279555

KEYWORD

nonn

AUTHOR

Megan A. Martinez, Dec 15 2016

EXTENSIONS

a(10)-a(20) from Alois P. Heinz, Feb 23 2017

STATUS

approved

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Last modified February 19 19:30 EST 2020. Contains 332047 sequences. (Running on oeis4.)