Common Lisp code basically equivalent to that first "trivial" Clojure implementation (WARNING: untested, may consist entirely of bugs): (defun factors (n)

Common Lisp code basically equivalent to that first "trivial" Clojure implementation (WARNING: untested, may consist entirely of bugs): (defun factors (n) (loop for r upfrom 1 to n when (zerop (remainder n r)) collect r)) Clojure doesn't have much advantage in conciseness over CL here. It's just a matter of what approach the contributor chose to use.