Labelled Enumeration

The symbolic method discussed in Chap. 1 may not always be suitable in addressing enumeration problems in combinatorial classes where some natural way of distinguishing objects by its labels appears, for example in the class of permutations. In this chapter, the notion of labelled classes is introduced and the power and flexibility of the symbolic method will again be demonstrated in applications to count classes of permutations, set partitions, labelled trees, words and other combinatorial objects.