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def definition def or abbrev

endpoint_pairs_summing_to_21

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formal statement (Lean)

 110def endpoint_pairs_summing_to_21 : List (ℕ × ℕ) :=

proof body

Definition body.

 111  [(7, 14), (8, 13), (14, 7), (13, 8)]
 112  -- Note: 1+20, 6+15, 11+10 excluded because they use middle values or
 113  -- values outside the natural set. 20 and 15 are possible but form less
 114  -- natural chains (see analysis below).
 115
 116/-- There exist multiple valid endpoint pairs from the natural invariants.
 117    This is the heart of the openness: uniqueness cannot be proved without
 118    additional structural constraints. -/

depends on (12)

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