rw [Nat.sum_divisorsAntidiagonal fun d e : ℕ => ↑(μ d) * (ν e)⁻¹]
case a
s : Sieve
l : ℕ
hl : Squarefree l
hnu_nonzero : ν l ≠ 0
⊢ ∑ i ∈ l.divisorsAntidiagonal, ↑(μ i.1) * (ν i.2)⁻¹ = ∑ i ∈ l.divisors, (ν l)⁻¹ * (↑(μ i) * ν i)
case a
s : Sieve
l : ℕ
hl : Squarefree l
hnu_nonzero : ν l ≠ 0
⊢ ∑ i ∈ l.divisors, ↑(μ i) * (ν (l / i))⁻¹ = ∑ i ∈ l.divisors, (ν l)⁻¹ * (↑(μ i) * ν i)