

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
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OFFSET

2,5


LINKS

Table of n, a(n) for n=2..29.
W. M. B. Dukes, Tables of matroids
Crapo, Henry H.; Rota, GianCarlo; On the foundations of combinatorial theory. II. Combinatorial geometries, Studies in Appl. Math. 49 1970 109133. [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



