| ⊦ ar[m, a][n, b] = ar[n, b][m, a], m = n |
⊦ ar1 = ar2 ↔ # ar1 = # ar2 ∧ (∀ n. n < # ar1 → ar1[n] = ar2[n])
⊦ # ar[m, a][n, b] = # ar[n, b][m, a] ∧ (∀ n0. n0 < # ar[m, a][n, b] → ar[m, a][n, b][n0] = ar[n, b][m, a][n0]), m = n
Used terms: ar[n, b][m, a], ar[m, a][n, b]