The second Zagreb index for a graph with vertex count and vertex degrees for , ..., is defined by
where is the edge set of .
The second Zagreb index for a graph with vertex count and vertex degrees for , ..., is defined by
where is the edge set of .
Weisstein, Eric W. "Second Zagreb Index." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/SecondZagrebIndex.html