An upper bound on the sum of squares of degrees in a graph
Discrete Mathematics
Independence polynomials of k-tree related graphs
Discrete Applied Mathematics
Sharp bounds for Zagreb indices of maximal outerplanar graphs
Journal of Combinatorial Optimization
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For a graph G, the first Zagreb index M1 is equal to the sum of squares of the vertex degrees, and the second Zagreb index M2 is equal to the sum of the products of degrees of pairs of adjacent vertices. The Zagreb indices have been the focus of considerable research in computational chemistry dating back to Gutman and Trinajstić in 1972. In 2004, Das and Gutman determined sharp upper and lower bounds for M1 and M2 values for trees along with the unique trees that obtain the minimum and maximum M1 and M2 values respectively. In this paper, we generalize the results of Das and Gutman to the generalized tree, the k-tree, where the results of Das and Gutman are for k=1. Also by showing that maximal outerplanar graphs are 2-trees, we also extend a result of Hou, Li, Song, and Wei who determined sharp upper and lower bounds for M1 and M2 values for maximal outerplanar graphs.