Erdős Problem 677 #
Reference: erdosproblems.com/677
Erdős expected very few solutions for $M(n, k) = M(m, l)$, where $m \geq n + k$ and $l > 1$. The only solutions he knew were the following.
theorem
Erdos677.erdos_677
(m n k : ℕ)
:
k > 0 → m ≥ n + k → Finset.lcmInterval m k ≠ Finset.lcmInterval n k
Denote by $M(n, k)$ the least common multiple of the finite set $\{n+1, \dotsc, n+k\}$. Is it true that for all $m \geq n + k$, we get $M(m, k) \neq M(n, k)$?