let n be Nat; ( 67 divides n iff 67 divides (value (((digits (n,10)) /^ 1),10)) - (20 * ((digits (n,10)) . 0)) )
(digits (n,10)) /^ 1 = mid ((digits (n,10)),2,(len (digits (n,10))))
by Th3;
hence
( 67 divides n iff 67 divides (value (((digits (n,10)) /^ 1),10)) - (20 * ((digits (n,10)) . 0)) )
by Th70; verum