Note the the "floor" will increase by one everytime we encounter a perfect square
Floor ( sqrt 1) = 1
Floor (sqrt 4) = 2
Floor (sqrt 9) = 3
Floor ( sqrt 16) = 4
Floor (sqrt 25 ) = 5
So...we will have the following sium
1(3) + 2(5) + 3(7) + 4 ( 9) + 5 = 75
