sequenced-spiral

core.clj

(defn spiral [n]
  (let [amounts
        (drop 1
              (interleave
               (range n 0 -1)
               (range n 0 -1)))

        directions
        (cycle [[1 0] [0 1] [-1 0] [0 -1]])

        steps
        (mapcat (fn [a d] (repeat a d)) amounts directions)

        coords
        (reductions (fn [r v] (map + r v)) steps)

        values (map (fn [[x y]] (+ x (* n y))) coords)]
    values))