let n be Nat; :: thesis: Parity ((n + 1) !) = (Parity (n + 1)) * (Parity (n !))
Parity ((n + 1) !) = Parity ((n !) * (n + 1)) by NEWTON:15;
hence Parity ((n + 1) !) = (Parity (n + 1)) * (Parity (n !)) by NEWTON05:25; :: thesis: verum