My book has the question
Find the number of connected graphs with four vertices. (Draw them)
My understanding of connected graphs is that these are graphs were it is possible to get from every vertex in the graph to every other vertex in the graph.
But what I am trying to understand is why connected graphs like below don't count but the ones above do?
Edit: Graph c and h is isomorphic. Graph f and g is isomorphic. Isn't graph a and b isomorphic as well? And c is isomorphic with f?