; your code goes here
 
(defun all-indexes-1 (len numbers pattern)
  (if (null numbers)
      (list pattern)
      (let (patterns)
	(dolist (n numbers)
	  (setf patterns
		(nconc patterns
		       (all-indexes-1 len
				      (remove n numbers)
				      (cons n pattern)))))
	patterns)))
 
(defun all-indexes (len)
  (all-indexes-1
   len
   (loop for n below len collect n)
   nil))
 
(defun all-patterns (seq)
  (let ((len (length seq))
	(acc))
    (dolist (indexes (all-indexes len))
      (let ((new (make-sequence (type-of seq) len)))
	(loop for i from 0 by 1
	      for j in indexes
	      do
		 (setf (aref new i)
		       (aref seq j)))
	(push new acc)))
    acc))
 
(mapc #'print (all-patterns "abcd"))
 

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