0,3

See link for software to generate the sequence. The next item (for n=6) should be roughly 2^32 and within computational reach. n=7 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 (jvospost2(AT)yahoo.com), Jun 20 2006

D. Eppstein, Reverse search for antimatroids.

Yulia Kempner, Vadim E. Levit, Correspondence Between Two Antimatroid Algorithmic Characterizations

E.g. 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}.

Sequence in context: A046947 A002485 A099750 this_sequence A132558 A072113 A105433

Adjacent sequences: A119767 A119768 A119769 this_sequence A119771 A119772 A119773

nonn

David Eppstein (eppstein(AT)ics.uci.edu), Jun 19 2006