(loop i) ; i starts equal to 1
  (loop 1)
  (+ i (loop (+ 1 i)))
  (+ 1 (loop (+ 1 1)))
  (+ 1 (loop 2))  ; (loop 2) creates a new unique i equal to 2
  (+ 1 (+ i (loop (+ 1 i))))
  (+ 1 (+ 2 (loop (+ 1 2))))
  (+ 1 (+ 2 (loop 3))) ; (loop 3) creates a new unique i equal to 3
  (+ 1 (+ 2 (+ i (loop (+ 1 i)))))
  (+ 1 (+ 2 (+ 3 (loop (+ 1 3)))))
  (+ 1 (+ 2 (+ 3 (loop 4))))
  ;; etc.