Do you recommend using a pan under washer?

It depends on where it is located. It could be a good idea if it has a drain in case of a leak.

If your washer is on the second floor, for sure you want a pan with an outside drain . First floor "not a bad idea. Basement, useless unless you can drain outside

That's a good way of saying it. Most people don't think of it until their ceiling falls in due to a leak.