Circular Benzenoids Perforated by Phenalene Hole

Assume that 0 N S) is a circular benzenoid which can be perforated by a phenalene hole to produce a single coronoid 0(n s). Then one has for the formula coefficients l T=n+l, 5=s — 3. All the isomers of the class 0 were enumerated. This is not a complete determination of the cardinalities because there always exist at least naphthalenic single coronoids with the 

The six characteristic shapes of circular benzenoids are recognized as in the case of circular single coronoids (Fig. 4.6), and are again indicated by the parameter e = 0,1, 2, 3, 4, 5. The smallest of the systems, which presently are associated with k = 0, are displayed in Fig. 4 three coronoids and three degenerate coronoids. All the C H formulas under consideration are given (in the Harary-Harborth picture) by 

In Table 8 a number of these formulas are collected, including those for s = 15, 16, 17, which pertain to the degenerate coronoids. 

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