Permanents of Hexagonal and Armchair Chains

The permanent is important invariants of a graph with some applications in physics. If G is a graph with adjacency matrix A=aij, then the permanent of A is defined as permA=∑σ∈Sn∏i=1naiσi, where Sn denotes the symmetric group on n symbols. In this paper, the general form of the adjacency matrices of hexagonal and armchair chains will be computed. As a consequence of our work, it is proved that if Gk and Hk denote the hexagonal and armchair chains, respectively, then permAG1=4, permAGk=k+12, k≥2, and permAHk=4k with k≥1. One question about the permanent of a hexagonal zig-zag chain is also presented.