A digraph topology on nodes is an unlabeled reflexivetransitive digraph, equivalently a preorder.
It corresponds to a finite topology; reflexive loops
may be suppressed in diagrams. The numbers of distinct topologies on , 2, ... nodes are 1, 3, 9, 33, 139, 718, 4535, ... (OEIS
A001930). Brinkmann and McKay (2005, p. 4)
computed these counts through .
nodes is an unlabeled reflexive transitive digraph, equivalently a preorder.
It corresponds to a finite topology; reflexive loops
may be suppressed in diagrams. The numbers of distinct topologies on 
, 2, ... nodes are 1, 3, 9, 33, 139, 718, 4535, ... (OEIS
A001930). Brinkmann and McKay (2005, p. 4)
computed these counts through 
.
