Department of Mathematics, College of Charleston, Charleston, South Carolina 29424
Abstract:
For a set of natural numbers, the structural properties are described when the upper asymptotic density of achieves the infimum of the upper asymptotic densities of all sets of the form , where the upper asymptotic density of is greater than or equal to the upper asymptotic density of . As a corollary, we prove that if the upper asymptotic density of is less than and the upper asymptotic density of achieves the infimum, then the lower asymptotic density of must be .