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Proof step 17 from proof nodups-butlastn (previous step)

a ∈ butlastn(n, x0), n ≤ # x0 ⊦ a ∈ x0

User applied rule structural induction

And obtained the following new goals

Proof step 18:
a ∈ butlastn(n, a0 + x), n ≤ #(a0 + x), ∀ a, n. a ∈ butlastn(n, x) ∧ n ≤ # x → a ∈ x ⊦ a ∈ a0 + x

Rule argument

indvar: x0

Additional information

Used simplifier rules: butlastN-base: ⊦ butlastn(0, x) = x;%list freely generated by [], +;;% ⊦ # [] = 0; (s)% ⊦ m ≤ 0 ↔ m = 0; (s)% ⊦ ¬ a ∈ []; (s)