We study the Dirichlet
polynomial PG(s) of the groups G =PSL(2,q), 2B2(q), and 2G2(q). For such G we
show that if H is a group satisfying PH(s) = PG(s), then H∕Frat(H)≅G. We
also prove that, when q is not a prime number, PG(s) is irreducible in the
ring of Dirichlet polynomials. Finally, we prove that the coset poset of G is
noncontractible.