I'm not familiar with the terminology of graph theory, since I have only worked with directed graphs the way they are usually defined in algebra: $$E= (E^0, E^1, r, s)$$ where $E^0$ is the set of vertices, $E^1$ is the set of edges, $r: E^1 \to E^0$ is a function assigning a range to every edge, and $S: E^1 \to E^0$ is a function assigning a source to every edge.
I am interested to know the meaning of this sequence, the number of oriented trees with $n$ nodes. Can anybody help?
Does an oriented tree have a single source and multiple sinks, or may it have multiple sources and multiple sinks?
Is a node the same thing as a vertex?
When are two oriented trees considered the same?