I almost had -ƝÆṛ⁼ for codegolf.stackexchange.com/questions/235366/… but it turns out Æṛ crashes on an empty input

if it returned [1] (which would be a sensible thing for it to return) it would be valid!

@Lynn I had sort of the opposite before realising that it fails for single element inputs :/

yeah, actually it fails for any multiple of a valid row

I believe the equivalent J builtin returns (highest coefficient ; roots) so that there's an actual sort of bijection