{"id":"seen-set-insert-after-check","text":"In `count_arithmetic_triplets`, each element is added to `seen` after the triplet membership check, maintaining the invariant that only previously-visited elements are lookup candidates","truth_value":"IN","source":"entries/2026/06/06/number-of-arithmetic-triplets-solution.md","source_url":"","source_hash":"","justifications":[],"dependents":[],"metadata":{},"created_at":"","updated_at":"","reviewed_at":"","verified_at":"","retracted_at":"","explanation":{"steps":[{"node":"seen-set-insert-after-check","truth_value":"IN","reason":"premise"}]}}