procedure Primz(maxzahl: longint; ts: TStrings);  
var x, y, z, i: longint;  
  a: array of longint;  
  procedure dazu;  
  begin  
    i := length(a);  
    setlength(a, i + 1);  
    a[i] := z;  
  end;  
begin  
  ts.clear;  
  if maxzahl >= 2 then begin  
    a := nil;  
    z := 2;  
    dazu;  
    x := 3;  
    while x <= maxzahl do begin  
      y := 0;  
      while y <= i do begin  
        z := x mod a[y];  
        if z = 0 then y := i + 1 else inc(y);  
      end;  
      if z <> 0 then begin  
        z := x;  
        dazu;  
      end;  
      inc(x, 2);  
    end;  
    for x := 0 to length(a) - 1 do ts.add(inttostr(a[x]));  
    a := nil;  
  end;  
end;  
 
 
// Beispielaufruf 
 
procedure TForm1.Button1Click(Sender: TObject);  
begin  
  button1.enabled := false;  
  primz(5000, Listbox1.Items);  
  button1.enabled := true;  
end;