subsets of size 2 and subsets of size 3 in python

i need a function that Displays the list of all unordered subsets of 2 elements from {1 to n} and returns the number of displayed subsets (same question for 3 elements) for example:

>>> subsets_2(1)
    0
>>> subsets_2(2)
    {1,2}
    1
>>> subsets_2(3)
    {1,2}
    {1,3}
    {2,3}
    3
>>> subsets_2(4)
    {1,2}
    {1,3}
    {1,4}
    {2,3}
    {2,4}
    {3,4}
    6

and for 3 elements:

>>> subsets_3(1)
    0
>>> subsets_3(2)
    0
>>> subsets_3(3)
    {1,2,3}
    1
>>> subsets_3(4)
    {1,2,3}
    {1,2,4}
    {1,3,4}
    {2,3,4}
    4
>>> subsets_3(5)
    {1,2,3}
    {1,2,4}
    {1,2,5}
    {1,3,4}
    {1,3,5}
    {1,4,5}
    {2,3,4}
    {2,3,5}
    {2,4,5}
    {3,4,5}
    10