theorem
proved
term proof
middle_pair_unique_nonzero
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formal statement (Lean)
90theorem middle_pair_unique_nonzero :
91 ∀ (b c : ℕ), b ∈ natural_invariants_D3 → c ∈ natural_invariants_D3 →
92 b + c = 17 → b ≠ c → b ≠ 0 → c ≠ 0 →
93 (b = 6 ∧ c = 11) ∨ (b = 11 ∧ c = 6) := by
proof body
Term-mode proof.
94 intro b c hb hc hsum hne hb0 hc0
95 have h := middle_pairs_are_11_6 b c hb hc hsum hne
96 rcases h with h | h | h | h
97 · exact Or.inl h
98 · exact Or.inr h
99 · exact absurd h.2 hc0
100 · exact absurd h.1 hb0
101
102/-! ## Constraint 2: Endpoint pair (a, d) sums to 21
103
104From the partition constraint a + 2b + 2c + d = 55 with b+c = 17:
105a + 34 + d = 55, so a + d = 21.
106-/
107
108/-- All pairs (a, d) from natural invariants with a + d = 21,
109 excluding {11, 6} (already used as middle) and ordered pairs. -/