Alex Chengyu Li

Erdős Problem 848: A Kernel-Checked Proof of the Exact Extremal Bound

For every integer N ≥ 1, the maximum cardinality of a set A contained in [1,N] for which ab+1 is nonsquarefree for every a,b in A is exactly the number of integers n ≤ N with n ≡ 7 (mod 25). The proof uses an exact Hall reformulation, an exact prefix-colouring certificate through...