%I A119770
%S A119770 1,1,3,22,485,59386
%N A119770 Number of different antimatroids on n labeled items.
%C A119770 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.
%C A119770 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 (jvospost3(AT)gmail.com), Jun 
               20 2006
%H A119770 D. Eppstein, <a href="http://11011110.livejournal.com/58994.html">Reverse 
               search for antimatroids</a>.
%H A119770 Yulia Kempner, Vadim E. Levit, <a href="http://arXiv.org:math/0307013">
               Correspondence Between Two Antimatroid Algorithmic Characterizations</
               a>
%e A119770 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}.
%Y A119770 Sequence in context: A002485 A099750 A156512 this_sequence A153230 A132558 
               A072113
%Y A119770 Adjacent sequences: A119767 A119768 A119769 this_sequence A119771 A119772 
               A119773
%K A119770 nonn
%O A119770 0,3
%A A119770 David Eppstein (eppstein(AT)ics.uci.edu), Jun 19 2006