return [ [ 2, 3, 4, 5 ], [ 1, 5, 6, 7 ], [ 1, 7, 8, 9 ], [ 1, 9, 10, 11 ], 
  [ 1, 11, 12, 2 ], [ 2, 12, 13, 14 ], [ 2, 14, 15, 3 ], [ 3, 15, 16, 9 ], 
  [ 3, 8, 17, 4 ], [ 4, 17, 18, 19 ], [ 4, 19, 20, 5 ], [ 5, 20, 21, 6 ], 
  [ 6, 21, 22, 14 ], [ 6, 13, 23, 7 ], [ 7, 23, 24, 8 ], [ 8, 24, 25, 17 ], 
  [ 9, 16, 18, 10 ], [ 10, 17, 25, 26 ], [ 10, 26, 20, 11 ], 
  [ 11, 19, 27, 12 ], [ 12, 27, 28, 13 ], [ 13, 28, 29, 23 ], 
  [ 14, 22, 24, 15 ], [ 15, 23, 29, 16 ], [ 16, 29, 30, 18 ], 
  [ 18, 30, 27, 19 ], [ 20, 26, 28, 21 ], [ 21, 27, 30, 22 ], 
  [ 22, 30, 25, 24 ], [ 25, 29, 28, 26 ] ];
