Recall that a sequence 
is convergent if and only if is also a Cauchy sequence, which means to say that for any 
, we can find a sufficiently large 
for which
whenever both
and 
exceed .
But this never happens if we choose
and 
; under these conditions, we have
Therefore is not a Cauchy sequence and hence does not converge.
whenever both
But this never happens if we choose
Therefore