Sum of Distinct Count by column

Hello Everyone,

I am having trouble calculating sum of Distinct Count. Basically, I would like to calculate Distinct count regarding a different column. Here is the example:

Term                ID

Spring 15          1

Spring 15          2

Spring 15          1

Spring 16          1

Spring 16          1

Spring 16          3

Spring 17          4

Spring 17          1

My original formula is DISTINCTCOUNT(Table[ID]). But it gives a total number 4. However, I would like to calculate sum of distinct ID for every term. It should have,

-2 distinct count for Spring 15,

-2 distinct count for Spring 16

-2 distinct count for Spring 17.

So distinct count would be 6 instead of 4.

By the way, there is something to point out. I was eligible to get correct number with a complicated formula but my page should react when we filter with a slicer. When I have something like (="Spring 15"), it does not response when Spring 15 is unselected in slicer.

It is not as complicated as it is seen. To recap, distinct count should be calculated for every data in column "term".

Sorry for the long message. I hope I can solve my issue.