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.
InfoPlease explains that human skin weighs between  8 to 10 pounds in normal adults, with around 22 square feet of area. The skin is the largest organ in the body in terms of weight and area. One of the smallest organs in the body, the pineal gland, weighs around 0.2 gram, or 0.007 ounce. The pineal gland is in the center of the brain, according to Kids Discover. The parathyroid is between 0.004 and 0.006 ounce, or 0.12 to 0.18 gram.