I know that 17 is the minimum for a standard 9x9 (3x3 squares), but what about a 16x16 (4x4 squares) sudoku?
As the comments say, the smallest number of clues found for a 16x16 sudoku (with 4x4 squares) is 55. It has not been proven that this is the smallest number, but no one's found a better one yet. I suspect that less research into a minimum number has occurred for the larger variants because they are less common and would require more computing power to brute-force.
16×16(4×4) Sudoku: At least one puzzle with 55 clues has been created. It is not known if this is the fewest possible.
The example 55-clue Sudoku