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素直に再帰

(defun generate-primes (limit)
  (labels ((check (x prime)
             (cond ((endp prime)
                    t)
                   ((zerop (rem x (car prime)))
                    nil)
                   (t
                    (check x (cdr prime)))))
           (main (n x prime)
             (cond ((> x n)
                    (nreverse prime))
                   ((check x prime)
                    (main n (+ x 2) (cons x prime)))
                   (t
                    (main n (+ x 2) prime)))))
    (format t "~{ ~D~}~%" (main limit 3 (list 2)))))

素直にループ

(defun generate-primes (limit)
  (let ((prime nil))
    (push 2 prime)
    (do ((x 3 (+ x 2)))
        ((> x limit))
      (if (dolist (i prime t) (if (zerop (rem x i)) (return nil)))
          (push x prime)))
    (format t "~{ ~A~}~%" (nreverse prime))))