Non-Isomorph trees of a graph Please consider this graph !enter image description here How many non-Isomorph trees with 4 vertex has this graph? Is there any formula that show number of non-Isomorph trees with $n$ vertices? thanks

There are only two 4-node trees up to isomorphism: the straight line and the Y-shaped graph. The above graph contains both of them.

For the number of trees with $n$ vertices, Wikipedia links here : < .