Zhang-Zhang polynomials of various classes of benzenoid systems

The Zhang-Zhang(ZZ) polynomials (aka Clar covering polynomial) for several subclasses of catacondensed and pericondensed benzenoid systems have been computed using an automatic computer code developed in our group and described in [C.-P. Chou and H.A. Witek, MATCH Commun. Math. Comput. Chem., submitted]. General closed-form expressions for several series of catacondensed benzenoids and for the prolate rectangular pericondensed benzenoids have been obtained. The presented results suggest that general closed-form expressions for the ZZ polynomials of many classes of pericondensed benzenoid systems can be discovered by analysis of structural similarities between the ZZ polynomials of their subclasses. Methods and techniques of finding such similarities are outlined.