reserve a,b,c,d,x,j,k,l,m,n,o,xi,xj for Nat,
  p,q,t,z,u,v for Integer,
  a1,b1,c1,d1 for Complex;

theorem MOB16:
  for b be non trivial Nat, a be non zero Integer holds
    b |-count a <> 0 iff b divides a
proof
  let b be non trivial Nat, a be non zero Integer;
  b |-count |.a.| <> 0 iff b divides |.a.|
  proof
    b <> 1 & a <> 0 by NAT_2:def 1;
    hence thesis by NAT_3:27;
  end;
  hence thesis by INT_2:16;
end;
