Let's call the columns numerically from left to right 1...9, and the rows alphabetically from top to bottom A...I. We'll refer to a cell using its row letter, followed by the column number.
We are going to use
Let's consider the cells
They conform to that pattern, with
We are sure that
Now considering the cells
And then you'll be able to ...
Yes, this is a Sudoku where you need slightly trickier techniques.
You have very few spaces in the middle row of boxes. They are mostly linked, so if you were able to fill in one of those cells, the rest would follow. After that, the first obvious cell you would be able to fill in would be cell C7 (third row, seventh column) because at that point it would ...
As long as there is a single Sudoku with 17 clues and a unique solution, the answer to your question is 17. And this paper has an example of such a puzzle, and its unique solution:
I was afraid this might end up needing some advanced trickery to complete, so I ran it through the online Sudoku 9x9.com solver. It made quick work of this, arriving at the (...