@a_list = (
  [1,2], [1,3], [1,4], [1,5],
  [2,3], [2,4],
  [3,4],
  [5,6], [5,7], [5,9],
  [6,9],
  [7,8],
  [8,9],
 );

##</code><code>##

1 2 3
1 2 4
1 3 4
2 3 4
5 6 9