refine coprime_of_squarefree_mul (hn.squarefree_of_dvd ?_)
case refine_3
n : ℕ
hn : Squarefree n
a : Fin 3 → ℕ
ha : a ∈ finMulAntidiagonal 3 n
⊢ (a 1).Coprime (a 2)
case refine_3
n : ℕ
hn : Squarefree n
a : Fin 3 → ℕ
ha : a ∈ finMulAntidiagonal 3 n
⊢ a 1 * a 2 ∣ n