Application of Redfield-Plya's Theorem to the enumeration of the substitution isomers of linear polycyclic aromatic hydrocarbons

In this brief work, we shall obtain the general formulae for the enumeration of the linear polycyclic aromatic hydrocarbons isomers when the hydrogen atom or the CH group is substituted by one or more atoms or different groups (substitution isomers). Such formulae have been derived from Redfield-Plya's Theorem (Burnside in Theory of groups of finite order. Cambridge University Press, Cambridge, 1897; Redfield in Am J Math 49:433, 1927) application.