push_cast
⊢ ∑ x ∈ Finset.range 330, ↑(∏ j ∈ (Finset.range 330).erase x, (660 + j) * (1319 - j)) =
    ↑(∑ i ∈ Finset.range 330, ∏ j ∈ (Finset.range 330).erase i, (660 + j) * (1319 - j))
⊢ ∑ x ∈ Finset.range 330, ∏ x ∈ (Finset.range 330).erase x, (660 + ↑x) * ↑(1319 - x) =
    ∑ x ∈ Finset.range 330, ∏ x ∈ (Finset.range 330).erase x, (660 + ↑x) * ↑(1319 - x)