b21 := (1,2,4)(3,5,8)(6,9,13)(7,10,15)(11,16,22)(12,17,24)(14,19,27)(18,25,32)
     (20,28,35)(21,29,37)(23,31,40)(26,33,43)(30,38,48)(34,44,52)(36,46,42)
     (39,49,55)(41,50,47)(45,53,58)(51,57,54)(56,60,64)(59,61,63)(62,65,66);