On extremal k-CNF formulas

In this paper, we consider the problem to determine the extremal formulas achieving this bound. We give a class of such formulas that contains a double exponential (in k) number of non-isomorphic ones. This class captures all formulas, with only one exception, that we have obtained so far. We also give the complete list for k=2 and 3 as well as several structural properties of such extremal formulas.