  We define the Grothendieck group of an n-angulated category and show that for
odd n its properties are as in the special case of n=3, i.e. the triangulated
case. In particular, its subgroups classify the dense and complete n-angulated
subcategories via a bijective correspondence. For a tensor n-angulated
category, the Grothendieck group becomes a ring, whose ideals classify the
dense and complete n-angulated tensor ideals of the category.
