| ∀ n, a. nextl(n, a) ≠ [] ∧ nextl(n, a).head = a ⊦ ∃ σ, ii. ii(0) = 0 ∧ σ(0) = a ∧ σ ≠ [] ∧ (∀ n. ii(n + 1) = ii(n) + # nextl(n, σ(ii(n))) - 1 ∧ ⌜ii(n + 1)⌝ < # σ ∧ σ.drop(ii(n)).take(# nextl(n, σ(ii(n)))) = nextl(n, σ(ii(n)))) ∧ (finp(σ) ⊃ ∃ n. # σ = ⌜ii(n) + 1⌝ ∧ (∀ m. n ≤ m → nextl(m, σ(ii(m))) = (σ(ii(m)))' ∧ ii(n) = ii(m));∀ n. ∃ m. ii(m) ≤ n ∧ n < ii(m + 1)) |