| dups(butlastn(n, a ' + x0)), n ≤ 1 + # x0, ∀ n0. ¬ dups(butlastn(n0, x0)) ∨ ¬ n0 ≤ # x0 ⊦ dups(x0), a ∈ x0 |
⊦ n ≤ # x → butlastn(n, a ' + x) = a ' + butlastn(n, x)
dups(butlastn(n, a ' + x0)), n ≤ 1 + # x0, ∀ n0. ¬ dups(butlastn(n0, x0)) ∨ ¬ n0 ≤ # x0 ⊦ dups(x0), a ∈ x0, n ≤ # x0
dups(a ' + butlastn(n, x0)), n ≤ 1 + # x0, n ≤ # x0, ∀ n0. ¬ dups(butlastn(n0, x0)) ∨ ¬ n0 ≤ # x0 ⊦ dups(x0), a ∈ x0
Used terms: x0, a, n