I've derived an expression for $P\{\lfloor X\rfloor= n, X -\lfloor X\rfloor\leq x\}$ to be $e^{-\lambda(n)}[1 - e^{-\lambda(x)}]$,
and when I find an expression for $P(\lfloor X\rfloor= n)P(X \leq x+n)$,
I have the two expressions aren't equal. Is this enough to say they aren't independent?