Abstract
Let Γ be a torsion-free finite-index subgroup of SLn(Z) or GLn(Z), and let υ be the cohomological dimension of Γ. We present an algorithm to compute the eigenvalues of the Hecke operators on Hυ–1(Γ; Z), for n = 2, 3, and 4. In addition, we describe a modification of the modular symbol algorithm of Ash and Rudolph for computing Hecke eigenvalues on Hυ(Γ; Z).