For $|A| = n$, how small can the cofactor set $Q(A) = \{a / \gcd(a,b) : a, b \in A\}$ be? The answer is $h(n) = n^{1/2 + o(1)}$: a new upper bound $h(n) \le n^{1/2} \exp(O(\sqrt{\log n}))$ matches the classical lower bound.

How a contribution reaches this record

Seven steps, in four places.

1. 1

   Read the sources and their formal declarations.

   Public
2. 2

   Work on it, wherever you work.

   Your machine
3. 3

   Keep an Approach and its Attempts here.

   Needs an account
4. 4

   Attach evidence by its content root.

   Needs an account
5. 5

   Prepare an unsigned Submission draft.

   Needs an account
6. 6

   Sign it with your own key.

   Your machine
7. 7

   The Repository decides.

   The Repository