Pansu has shown that the growth function of every virtually nilpotent group
Gamma with respect to any finite generating set has asymptotics y(n) simil
ar to alpha n(d), where d is the degree of growth of Gamma. The paper refin
es his result in the special case of 2-step nilpotent groups to obtain y(n)
= alpha n(d) + O(n(d-1)).