⌜n0 +1⌝ < # nσ, stutf(nσ), ∀ nσ. ⌜n0⌝ < # nσ ∧ stutf(nσ) → (n0 < nσ[n0] ↔ false) ⊦ n0 +1 < nσ[n0 +1] ↔ false
Used simplifier rules: stutf-zero: ⊦ stutf(nσ) → nσ[0] = 0;%nat freely generated by 0, +1;;