theorem
proved
term proof
middle_pairs_are_11_6
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formal statement (Lean)
78theorem middle_pairs_are_11_6 :
79 ∀ (b c : ℕ), b ∈ natural_invariants_D3 → c ∈ natural_invariants_D3 →
80 b + c = 17 → b ≠ c →
81 (b = 6 ∧ c = 11) ∨ (b = 11 ∧ c = 6) ∨
82 -- Any other pair summing to 17 among our natural invariants
83 (b = 17 ∧ c = 0) ∨ (b = 0 ∧ c = 17) := by
proof body
Term-mode proof.
84 intro b c hb hc hsum _hne
85 simp [natural_invariants_D3, List.mem_cons] at hb hc
86 omega
87
88/-- Excluding zero (since 0 is not a "natural cube invariant"), only
89 {11, 6} appears in the middle pair position. -/