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

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
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
...

Crossrefs

Diagonals give A063800-A063803, A246988, A246989. Row sums give A063805. For nondegenerate matroids see A063851.

Sequence in context: A327083 A104002 A073135 * A213800 A224823 A078753

Adjacent sequences: A063801 A063802 A063803 * A063805 A063806 A063807

Keyword

nonn,tabl,nice,more

Author

N. J. A. Sloane, Aug 20 2001

Status

approved