It works, at least to 1000 x 1000...and I don't see why it wouldn't work infinitely =)

It also works to produce unique identifiers for reversible combinations of more than two integers, like this:

[unique floating id from a set of three integers]
(a^2+b^2+c^2)+( sin(atan(a/b))*cos(atan(a/b))*sin(atan(a/c))*cos(atan(a/c))*sin(atan(b/c))*cos(atan(b/c)) )

Solved!