Generalized Lefschetz numbers of pushout maps

There is a useful way of defining a new map f from other given maps f(A), f(1) and f(2) the pushout construction. The pushout map f is analogous to the well known pushout of topological spaces. In this paper we prove a Pushout formula relating the generalized Lefschetz number of the pushout map f to those of the given maps f(A), f(1) and f(2). This provides a tool to compute generalized Lefschetz numbers and Nielsen numbers in a rather easy way. Some interesting examples are given at the end of the paper.