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A058730 Triangle T(n,k) giving number of nonisomorphic simple matroids of rank k on n labeled points (n >= 2, 2<=k<=n). 4
1, 1, 1, 1, 2, 1, 1, 4, 3, 1, 1, 9, 11, 4, 1, 1, 23, 49, 22, 5, 1, 1, 68, 617, 217, 40, 6, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

2,5

LINKS

Table of n, a(n) for n=2..29.

W. M. B. Dukes, Tables of matroids

Crapo, Henry H.; Rota, Gian-Carlo; On the foundations of combinatorial theory. II. Combinatorial geometries, Studies in Appl. Math. 49 1970 109-133. [Annotated scanned copy of pages 126 and 127 only]

W. M. B. Dukes, Counting and Probability in Matroid Theory, Ph.D. Thesis, Trinity College, Dublin, 2000.

Index entries for sequences related to matroids

W. M. B. Dukes, On the number of matroids on a finite set

EXAMPLE

Triangle begins:

1,

1, 1,

1, 2, 1,

1, 4, 3, 1,

1, 9, 11, 4, 1,

1, 23, 49, 22, 5, 1,

1, 68, 617, 217, 40, 6, 1.

...

CROSSREFS

Cf. A058720. Row sums give A002773. Diagonals give A058731, A058733.

Sequence in context: A125781 A091150 A091351 * A112705 A070895 A127054

Adjacent sequences:  A058727 A058728 A058729 * A058731 A058732 A058733

KEYWORD

nonn,tabl,nice,more

AUTHOR

N. J. A. Sloane, Dec 31 2000

STATUS

approved

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Last modified January 17 14:12 EST 2019. Contains 319225 sequences. (Running on oeis4.)