  A nilpotent Lie algebra n_{n,1} with an (n-1) dimensional Abelian ideal is
studied. All indecomposable solvable Lie algebras with n_{n,1} as their
nilradical are obtained. Their dimension is at most n+2. The generalized
Casimir invariants of n_{n,1} and of its solvable extensions are calculated.
For n=4 these algebras figure in the Petrov classification of Einstein spaces.
For larger values of n they can be used in a more general classification of
Riemannian manifolds.
