Exact extremal size of divisor-difference-free sets

Determine the exact value of F(n;t), the maximum cardinality of a subset A of {1,...,n} such that no two elements a<b in A with b-a at least t satisfy b-a dividing b.

Background

The paper proves the asymptotic upper bound F(n;t)=(1/2+o_t(1))n for each fixed t, resolving the asymptotic question posed by Erdős. It explicitly distinguishes this from the unresolved problem of determining the exact value of F(n;t).