

A119770


Number of different antimatroids on n labeled items.


1




OFFSET

0,3


COMMENTS

See link for software to generate the sequence. The next item (for n=8) should be roughly 2^78 and seems hopeless without more mathematics.
Antimatroids are a subset of greedoids, usually defined either in terms of set systems, as David Eppstein does in his tree searches, or in terms of formal languages. The two are equivalent, as discussed in Kempner and Levit.  Jonathan Vos Post, Jun 20 2006


LINKS



EXAMPLE

The three antimatroids on the two items 0 and 1 are (a) {},{0},{0,1}, (b) {},{1},{0,1} and (c) {},{0},{1},{0,1}.


CROSSREFS

Cf. A224913 (counts antimatroids, taking symmetries into account).


KEYWORD

nonn,more


AUTHOR



EXTENSIONS

Term for n=6 added based on a computer search by Przemysław Uznański  David Eppstein, Feb 26 2013
Term for n=7 added by Przemyslaw Uznanski, computed by Przemysław Uznański and Michał Bartoszkiewicz, Apr 19 2013


STATUS

approved



