Ordered triples

Write a procedure to find all ordered triples of distinct positive integers i , j , and k less than or equal to a given integer n that sum to a given integer s .

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Run

(check-equal? (make-triple-sum 4 6) '((3 2 1)))
(check-equal? (make-triple-sum 3 6) '((3 2 1)))
(check-equal? (length (make-triple-sum 9 9)) 3)