SQL Server 2012 :: Obtaining A Comma Delimited List For Each Group In The Output Of A Group By Query?

I'd like to ask how you would get the OUTPUT below from the TABLE below:

TABLE:
id category
1 A
2 C
3 A
4 A
5 B
6 C
7 B

OUTPUT:

category count id's
A 3 1,3,4
B 2 5,7
C 2 2,6

The code would go something like:

Select category, count(*), .... as id's
from TABLE
group by category

I just need to find that .... part.