f(n)=min{max S :|S|=n and S has distinct subset sums}?
Erdos conjectures that f(n) > c2^n for some constant c. In 1967 Conway and Guy constructed an interesting sequence of sets of integers. They conjectured not only that these sets have distinct subset sums but also that they are the best possible (with respect to the largest element). I will show a technique for proving that sets of integers have distinct subset sums. This technique can be used to show that the sets from the Conway-Guy sequence (as well as some other interesting sets) have distinct subset sums. The Conway-Guy sequence now gives the best known upper bound on f(n).