We consider a parametric semilinear Dirichlet problem with an unbounded and indefinite potential. In the reaction we have the competing effects of a sublinear (concave) term and of a superlinear (convex) term. Using variational methods coupled with suitable truncation techniques. we prove two multiplicity theorems for small values of the parameter. https://www.parisnaturalfoodes.shop/product-category/bio-chlorella/