amcnamara's solution to https://4clojure.com/problem/138

gistfile1.clj

(fn [s e]
  (let [squares   (apply str (take-while #(<= % e) (iterate #(* % %) s)))
        filler    (drop (count squares) (repeat (#(* % %) (Math/ceil (Math/sqrt (count squares)))) \*))
        elements  (concat squares filler)
        dimension (int (Math/sqrt (count elements)))
        cardinal  (- (* 2 dimension) 1)
        canvas    (vec (repeat cardinal ""))
        start-pos (* 2 (quot (dec dimension) 2))
        path      (take (count elements) (mapcat #(repeat (+ 2 (* 2 %)) (if (odd? %) dec inc)) (range)))
        balance   (fn [c] (#(apply str `(~@% ~@(interpose \  c) ~@%)) (repeat (/ (- cardinal (- (* 2 (count c)) 1)) 2) \ )))]
    (map balance
      ((fn [canvas row [element & rest-elts] [move & rest-path]]
         (if (nil? element)
           canvas
           (recur (update-in canvas [row] #(if (= move inc) `(~@% ~element) `(~element ~@%)))
                  (move row)
                  rest-elts
                  rest-path)))
       canvas
       start-pos
       elements
       path))))