b11 := (2,4)(3,6)(5,9)(7,11)(8,13)(10,16)(12,17)(15,20)(18,24)(19,25)(21,27)
     (23,29)(26,34)(28,37)(30,38)(31,40)(33,41)(35,44)(36,45)(39,47)(42,49)
     (43,50)(46,51)(48,52);