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A063851 Triangle T(n,k) (n >= 3, k = 1..n-2) read by rows  giving number of nonisomorphic nondegenerate oriented matroids with n points in n-k dimensions. 5
1, 1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 11, 11, 1, 1, 1, 135, 2628, 135, 1, 1, 1, 4382, 9276601, 9276601, 4382, 1, 1, 1, 312356 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

3,10

REFERENCES

Lukas Finschi, A Graph Theoretical Approach for Reconstruction and Generation of Oriented Matroids, A dissertation submitted to the Swiss Federal Institute of Technology, Zurich for the degree of Doctor of Mathematics, 2001.

Fukuda, Komei; Miyata, Hiroyuki; Moriyama, Sonoko. Complete Enumeration of Small Realizable Oriented Matroids. Discrete Comput. Geom. 49 (2013), no. 2, 359--381. MR3017917. - From N. J. A. Sloane, Feb 16 2013 [Beware typos in Table 1.]

LINKS

Table of n, a(n) for n=3..34.

L. Finschi, Homepage of Oriented Matroids

L. Finschi and K. Fukuda, Complete combinatorial generation of small point set configurations and hyperplane arrangements, pp. 97-100 in Abstracts 13th Canadian Conference on Computational Geometry (CCCG '01), Waterloo, Aug. 13-15, 2001.

EXAMPLE

Triangle begins:

1

1,1,

1,1,1,

1,1,1,4,

1,1,1,11,11,

1,1,1,135,2628,135,

1,1,1,4382,9276601,9276601,4382,

1,1,1,312356,...

CROSSREFS

For numbers when degenerate matroids are included see A063804. Rightmost diagonal gives A006248. Row sums give A063852.

Sequence in context: A113196 A037291 A222317 * A124777 A203639 A265679

Adjacent sequences:  A063848 A063849 A063850 * A063852 A063853 A063854

KEYWORD

nonn,tabl,nice,more

AUTHOR

N. J. A. Sloane, Aug 26 2001

EXTENSIONS

More terms taken from Fukuda et al., 2013. - N. J. A. Sloane, Feb 16 2013

STATUS

approved

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Last modified April 20 14:27 EDT 2019. Contains 322310 sequences. (Running on oeis4.)