rw [Icc_eq_cons_Ioc hN, Finset.sum_cons, divisors_one, sum_singleton, moebius_apply_one]
N : ℕ
hN : 1 ≤ N
this : ∀ {N : ℕ}, 1 N = ∑ d ∈ N.divisors, μ d
⊢ 1 = ↑(∑ m ∈ Icc 1 N, ∑ d ∈ m.divisors, μ d)
N : ℕ
hN : 1 ≤ N
this : ∀ {N : ℕ}, 1 N = ∑ d ∈ N.divisors, μ d
⊢ 1 = ↑(1 + ∑ x ∈ Ioc 1 N, ∑ d ∈ x.divisors, μ d)