Let s_k be the number of independent vertex sets of cardinality k in a graph G. The polynomial I(x) = sum_(k = 0)^(α(G)) s_k x^k, where α(G) is the independence number, is called the independence polynomial of G (Gutman and Harary 1983, Levit and Mandrescu 2005). It is also goes by several other names, including the independent set polynomial or stable set polynomial.