Omega subgroups of powerful p-groups

Abstract

Let G be a powerful finite p-group. In this note, we give a short elementary proof of the following facts for all i ≥ 0: (i) exp Ωi(G) ≤ p i for odd p, and expΩi(G) ≤ 2 i+1 for p = 2; (ii) the index |G: G p i| coincides with the number of elements of G of order at most p i.