theorem
proved
term proof
mobius_eq_zero_iff_not_squarefree
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formal statement (Lean)
50theorem mobius_eq_zero_iff_not_squarefree {n : ℕ} : mobius n = 0 ↔ ¬Squarefree n := by
proof body
Term-mode proof.
51 -- Negate `μ n ≠ 0 ↔ Squarefree n`.
52 simpa [not_ne_iff] using (not_congr (mobius_ne_zero_iff_squarefree (n := n)))
53
54/-- If `n` is squarefree then `μ n = (-1)^(cardFactors n)`. -/