return [ rec(
      invers := ( 1, 5)( 2,11)( 3,19)( 4, 8)( 6,14)( 7,12)( 9,18)(10,15)(13,17)(16,20),
      nbP := 20,
      next := ( 1, 2, 3, 4)( 5, 6, 7)( 8, 9,10)(11,12,13)(14,15,16,17)(18,19,20) ), rec(
      invers := ( 1, 4)( 2,11)( 3, 8)( 5,10)( 6,20)( 7,14)( 9,17)(12,16)(13,18)(15,19),
      nbP := 20,
      next := ( 1, 2, 3)( 4, 5, 6, 7)( 8, 9,10)(11,12,13)(14,15,16)(17,18,19,20) ) ];
