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A063804

Triangle T(n,k) (n >= 3, k = 1..n-2) read by rows, giving number of nonisomorphic oriented matroids with n points in n-k dimensions.

1, 1, 2, 1, 3, 4, 1, 4, 12, 17, 1, 5, 25, 206, 143, 1, 6, 50, 6029, 181472, 4890, 1, 7, 91, 508321

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OFFSET

3,3

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

LINKS

Table of n, a(n) for n=3..27.

Lukas 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 2

1 3 4

1 4 12 17

1 5 25 206 143

1 6 50 6029 181472 4890

1 7 91 508321 unknown unknown 461053