SQL & PL/SQL

I have a table like this :

 Day, Qty
 10, 1
 11, 1
 12, 1
 13, 1
 14, 1
 

The output that I need to create is a summary data like:

 Day_List, Qty
  10,       1
  11,       1
  12,       1
  13,       1
  14,       1
  10_11,    2
  11_12,    2
  12_13,    2
  13_14,    2
  10_11_12, 3
  11_12_13, 3
  12_13_14, 3
 

The aggregate data will comprise for any 2 or 3 consecutive days. Thank you,

Kumar