have h1 : (((1319 - i):ℕ):ℚ) = 1319 - (i:ℚ) := by
  have : i ≤ 1319 := by omega
  simp_all only [Nat.cast_sub, Nat.cast_ofNat]
i : ℕ
hi : i < 330
⊢ (∏ x ∈ (Finset.range 330).erase i, (660 + ↑x) * ↑(1319 - x)) * ((660 + ↑i) * ↑(1319 - i)) /
      ((660 + ↑i) * (1319 - ↑i)) =
    ∏ x ∈ (Finset.range 330).erase i, (660 + ↑x) * ↑(1319 - x)
i : ℕ
hi : i < 330
h1 : ↑(1319 - i) = 1319 - ↑i
⊢ (∏ x ∈ (Finset.range 330).erase i, (660 + ↑x) * ↑(1319 - x)) * ((660 + ↑i) * ↑(1319 - i)) /
      ((660 + ↑i) * (1319 - ↑i)) =
    ∏ x ∈ (Finset.range 330).erase i, (660 + ↑x) * ↑(1319 - x)