What happens: n Hall effect sensors wired in parallel, < n of them is triggered?
The sensors you linked are all open collector or open drain, so they pull their output low, and depend on an external resistor to pull the output high.

You can connect all the outputs together, with a single pull-up resistor, to the Arduino input.  If the Arduino input has an internal pull-up resistor, you may not need an external pull-up.

The total output leakage current of the sensors may determine the need for an external pull-up resistor, or may limit the number of sensors you can connect in parallel for reliable operation.