English
The maximal ideal equals the ideal generated by 2 and 3: maximalIdeal ℕ = span {2,3}.
Русский
Максимальный идеал ℕ равен идеалу, порождаемому числами 2 и 3: maximalIdeal ℕ = span {2,3}.
LaTeX
$$$\maximalIdeal \mathbb{N} = \mathrm{span}\{2,3\}$$$
Lean4
theorem maximalIdeal_eq_span_two_three : maximalIdeal ℕ = span { 2, 3 } :=
by
refine le_antisymm (fun n h ↦ ?_) (span_le.mpr <| Set.pair_subset (by simp) (by simp))
obtain lt | lt := (mem_maximalIdeal_iff.mp h).lt_or_gt
· obtain rfl := lt_one_iff.mp lt; exact zero_mem _
exact mem_span_pair.mpr <| exists_add_mul_eq_of_gcd_dvd_of_mul_pred_le 2 3 n (by simp) (show 2 ≤ n by cutsat)