Orientations of hexagonal chains with extremal values of the Randić index.

Let D be a digraph with set of vertices V(D) and set of arcs A(D). Recently, the Randić index of D was extended to digraphs as1RD=12∑uv∈AD1dD+udD−v,where dD+u and dD−v are the out‐degree and in‐degree of u and v, respectively. In this paper we study the extremal values of R over the set of all orientations of hexagonal chains with k hexagons. [ABSTRACT FROM AUTHOR]