DouKaku?

(use srfi-1)
(use util.combinations)
(define (maho n)
  (define (maho-in m l)
    (if (= m 0) 1
      (letrec
       ((cn (/ (* n (+ (* n n) 1)) 2))
        (mylist
         (map (lambda (li) (cons (car l) li))
              (filter
               (lambda (li) (= (apply + li) (- cn (car l))))
               (combinations (cdr l) (- n 1))))))
       (apply + (map (lambda (a) (maho-in (- m n) (lset-difference equal? l a))) mylist)))))
  (maho-in (* n n) (iota (* n n) 1)))

(define (maho-by-enm n)
  (define (center n) (/ (* n (+ (* n n) 1)) 2))
  (define (flatten2 l c)
    (define (flatten1 l c)
      (if (null? l) c
        (cons (car l) (flatten1 (cdr l) c))))
    (if (null? l) c
      (flatten2 (cdr l) (flatten1 (car l) c))))
  (define (my-equal? l1 l2)
    (null? (lset-xor eq? (flatten2 l1 '()) l2)))
  (define (enm-n n)
    (filter (lambda (l) (= (apply + l) (center n)))
            (combinations (iota (* n n) 1) n)))
  (filter (lambda (l) (my-equal? l (iota (* n n) 1)))
          (combinations (enm-n n) n)))