Enumeration of labeled outerplanar bicyclic and tricyclic graphs

The class of outerplanar graphs is used for testing the average complexity of algorithms on graphs. A random labeled outerplanar graph can be generated by a polynomial algorithm based on the results of an enumeration of such graphs. By a bicyclic (tricyclic) graph we mean a connected graph with cyclomatic number 2 (respectively, 3). We find explicit formulas for the number of labeled connected outerplanar bicyclic and tricyclic graphs with $n$ vertices and also obtain asymptotics for the number of these graphs for large $n$. Moreover, we obtain explicit formulas for the number of labeled outerplanar bicyclic and tricyclic $n$-vertex blocks and deduce the corresponding asymptotics for large $n$. Tab. 1, illustr. 4, bibliogr. 15.