Enumeration of semi-regular tessellations.

In this note we show how the semi-regular tessellations can be enumerated. We describe only the approach and give a partial solution. First we recall the definition: A semi-regular tessellation is ailing of the plane with regular polygons of two or more kinds, such that the polygons with a given number of sides are congruent copies of one another, and the pattern of placement of the polygons is the same at every vertex of the tessellation