for p being FinSequence
for x being object st p is one-to-one & x in rng p holds
for k being Nat st k in dom (p - {x}) holds
( ( (p - {x}) . k = p . k implies k < x .. p ) & ( k < x .. p implies (p - {x}) . k = p . k ) & ( (p - {x}) . k = p . (k + 1) implies x .. p <= k ) & ( x .. p <= k implies (p - {x}) . k = p . (k + 1) ) )