(defun fac (n)
  (labels
      ((f (m acc)
         (cond ((= m 0) acc)
               ('t (f (1- m) (* m acc))))))
    (f n 1)))

(defun string-to-list (str)
  (map 'list 'identity str))

(defun perms (ys k)
  (labels
      ((p (xs n acc)
         (if (null xs)
             (reverse acc)
             (let* ((m (fac (1- (length xs))))
                    (y (floor n m))
                    (x (nth y xs)))
               (p (delete x xs)
                  (mod n m)
                  (cons x acc))))))
    (p ys k nil)))

(concatenate 'string
             (perms (string-to-list "0123456789")
                    999999))

CL-USER> 
"2783915460"

— Me@2024-11-12 10:50:23 AM

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2024.11.12 Tuesday (c) All rights reserved by ACHK