(fact (primefactors 1) => (list))

(fact (primefactors 2) => (list 2))

(fact (primefactors 3) => (list 3))

(fact (primefactors 4) => (list 2 2))

(defn primefactors
    ([n] (primefactors n 2))
    ([n candidate]
        (cond (<= n 1) (list)
              (= 0 (rem n candidate)) (conj (primefactors (/ n candidate)) candidate)
              :else (primefactors n (inc candidate))
        )
    )
)

(fact (primefactors 1000001) => (list 101 9901))

(defn primefactors
  ([n]
    (primefactors n 2 '()))
  ([n candidate acc]
    (cond (<= n 1) (reverse acc)
          (zero? (rem n candidate)) (recur (/ n candidate) candidate (cons candidate acc))
          :else (recur n (inc candidate) acc))))

(defn primefactors
  ([n] (primefactors n 2 '()))
  ([n candidate acc]
    ...)

(primefactors n (inc candidate))

(recur n (inc candidate))

(primefactors (/ n candidate))