ext x
n : ℕ
⊢ image (⇑(piFinTwoEquiv fun x => ℕ)) (finMulAntidiagonal 2 n) = n.divisorsAntidiagonal
case a
n : ℕ
x : ℕ × ℕ
⊢ x ∈ image (⇑(piFinTwoEquiv fun x => ℕ)) (finMulAntidiagonal 2 n) ↔ x ∈ n.divisorsAntidiagonal