The problem is that you are reversing the string a few times. The following will do: (defun base8 (n) (let ((t8 (truncate n 8)) (m8 (mod n 8))) (if (= t8 0) (list m8) (append (base8 t8) (list m8))))) EDIT Here's a solution without append, using a helper function.
On average, a kidney weighs approximately 150 to 160 grams and, together, both kidneys weigh about 0.5 percent of total body weight. Usually, the left kidney is slightly larger than the right. These measurements and weights represent the typical ranges of a healthy, adult human kidney.
The kidneys are located in the back of the abdomen, one on each side of the spinal column, at about the level of the lower ribs. The average weight of an adult human kidney is approximately one-quarter pound. Each kidney is approximately 4 inches long, 2.5 inches wide, and 1.5 inches thick.