Enumeration: Numbers of Internal Vertices

In the preceding chapters the classification of the coronoids into cataconden-sed and pericondensed systems is taken into account. This means a classification according to n_i = 0 and n_i > 0, respectively, where n_i is the number of internal ver-tices. A more detailed classification of the pericondensed coronoid systems according to the values of n_i is also possible. This kind of classification, which is the subject of the present chapter, is of a particular chemical interest because it is virtually an enumeration of the chemical isomers. Some enumerations of this kind for coronoid systems, beyond the catacondensed coronoids, have been reported (Cyvin SJ and Brunvoll 1989; Dias 1990; Cyvin SJ, Brunvoll and Cyvin 1990b).