(* 6.9 *)
    1:  BEGIN  s:=0;
          FOR k := n DOWNTO 1 DO s := s + 1/k; s:= s-ln(n)
        END;
(* 6.10a) *)
    2:  BEGIN
           s :=0; FOR k:= n DOWNTO 1 DO s := s + sqr(1/k);
        END;
(* 6.10b) *)
    3: BEGIN  s :=0; (* aufpassen wegen integer Ueberlauf ! *)
          FOR k:= n DOWNTO 1 DO s := s + (1+1/k+1/k/k)/(3+1/k/k/k/k)/k/k;
          s := s+1;
       END;