Find the number of positive integers ${}n$ that satisfy $\lfloor \sqrt{n} \rfloor + \lfloor \sqrt{4n} \rfloor = 5.$
No positive integer n makes this true...
If n = 3
floor [ sqrt 3 ] + floor [ sqrt (4*3) ] = 1 + 3 = 4
If n = 4
floor [ sqrt 4] + floor [sqrt ( 4 *4) ] = 2 + 4 = 6
