See the adjacency matrix of one of the graphs shown by clicking on
the corresponding graph button.
Click 11 times on the "increase m" button to see the transitive closure.
Am denotes reachability where only paths
with only intermediate vertices 1,2,...m
We use the formula
am(i,j) = am-1(i,j) + am-1(i,m)*am-1(m,j)