(use srfi-1)
(use util.combinations)

(define (maho-memo n)
  ;tableに足してcnになるリストを入れておく
  (define table 
    (let ((cn (/ (* n (+ (* n n) 1)) 2)))
      (filter
       (lambda (li) (= (apply + li) cn))
       (combinations (iota (* n n) 1) n))))
  (define maho-in-memo
    (let1
     tab (make-hash-table 'equal?)
     (define (memo m l v) (hash-table-put! tab (cons m l) v) v)
     (lambda (m l)
       (cond ((= m 0) 1)
             ((hash-table-get tab (cons m l) #f))
             (else
              (memo m l
                    (apply
                     +
                     (map ; 今のlからaを除いたリストでmaho-in-memoを呼ぶ
                      (lambda (a) (maho-in-memo (- m n) (lset-difference equal? l a)))
                      (filter ;(car l)で始まるtableの中のリストを抜き出す
                       (lambda (li) (and (equal? (car li) (car l)) (lset<= equal? li l)))
                       table)))))))))
  (maho-in-memo (* n n) (iota (* n n) 1)))
(time (maho-memo 5))