swap
case pos
s : SelbergSieve
k n : ℕ
f : ℕ → ℝ
h : ∀ (l : ℕ), l ∣ n → ¬k ∣ l → f l = 0
hn : ¬n = 0
hkn : k ∣ n
⊢ ∑ l ∈ n.divisors, f l = ∑ m ∈ n.divisors, if k * m ∣ n then f (k * m) else 0

case neg
s : SelbergSieve
k n : ℕ
f : ℕ → ℝ
h : ∀ (l : ℕ), l ∣ n → ¬k ∣ l → f l = 0
hn : ¬n = 0
hkn : ¬k ∣ n
⊢ ∑ l ∈ n.divisors, f l = ∑ m ∈ n.divisors, if k * m ∣ n then f (k * m) else 0
case neg
s : SelbergSieve
k n : ℕ
f : ℕ → ℝ
h : ∀ (l : ℕ), l ∣ n → ¬k ∣ l → f l = 0
hn : ¬n = 0
hkn : ¬k ∣ n
⊢ ∑ l ∈ n.divisors, f l = ∑ m ∈ n.divisors, if k * m ∣ n then f (k * m) else 0

case pos
s : SelbergSieve
k n : ℕ
f : ℕ → ℝ
h : ∀ (l : ℕ), l ∣ n → ¬k ∣ l → f l = 0
hn : ¬n = 0
hkn : k ∣ n
⊢ ∑ l ∈ n.divisors, f l = ∑ m ∈ n.divisors, if k * m ∣ n then f (k * m) else 0