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.
Structure and Function of Kidney: Location of kidneys is of particular importance in your body. There are two bean shaped kidneys in the human body. A normal kidney is about 2.5 cm thick, 10 cm long and 5 cm wide. They are reddish-brown in color. Each weighs around 130 gm in adults. Both kidneys receive blood from the renal artery.