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Proof step 26 from proof nodups-butlastn (previous step)

n ≤ # x, a ∈ a0 ' + butlastn(n, x), n ≤ # x + 1, ∀ a, n. a ∈ butlastn(n, x) ∧ n ≤ # x → a ∈ x ⊦ a = a0, a ∈ x

Heuristic simplifier applied rule simplifier

And obtained the following new goals

Proof step 27:
n ≤ # x + 1, n ≤ # x, a ∈ butlastn(n, x), ∀ a, n. a ∈ butlastn(n, x) ∧ n ≤ # x → a ∈ x ⊦ a = a0, a ∈ x

Rule argument

Additional information

Used simplifier rules: a: ⊦ (x + y) + z = x + y + z; from specification list%in-01: ⊦ a ≠ b → (a ∈ b ' + x ↔ a ∈ x); from specification list