文摘
A finite group R is a \({\mathrm {DCI}}\)-group if, whenever S and T are subsets of R with the Cayley digraphs \({\mathrm {Cay}}(R,S)\) and \({\mathrm {Cay}}(R,T)\) isomorphic, there exists an automorphism \(\varphi \) of R with \(S^\varphi =T\). The classification of \({\mathrm {DCI}}\)-groups is an open problem in the theory of Cayley digraphs and is closely related to the isomorphism problem for digraphs. This paper is a contribution toward this classification, as we show that every dihedral group of order 6p, with \(p\ge 5\) prime, is a \({\mathrm {DCI}}\)-group. This corrects and completes the proof of Li et al. (J Algebr Comb 26:161-81, 2007, Theorem 1.1) as observed by the reviewer (Conder in Math review MR2335710). Keywords Cayley graph Isomorphism problem CI-group Dihedral group