Ordering chemical graphs by Randić and sum-connectivity numbers

摘要

Let G be a graph with edge set E(G). The Randić and sum-connectivity indices of G are defined as R(G)=∑uv∈E(G)1degG(u)degG(v) and SCI(G)=∑uv∈E(G)1degG(u)+degG(v), respectively, where degG(u) denotes the vertex degree of u in G. In this paper, the extremal Randić and sum-connectivity index among all n-vertex chemical trees, n ≥ 13, connected chemical unicyclic graphs, n ≥ 7, connected chemical bicyclic graphs, n ≥ 6 and connected chemical tricyclic graphs, n ≥ 8, were presented.