1 (defun enumerate-interval (low high)
2   (if (> low high)
3       nil
4       (cons low (enumerate-interval (1+ low) high))))
5 (defun flatpmap (proc seq)
6   (accumulate #'append nil (mapcar proc seq)))
7 (defun sum (lst)
8   (accumulate #'+ 0 lst))
9 (defun prime-sum? (pair)
10   (prime? (sum pair)))
11 (defun make-pair-sum (pair)
12   (list (car pair) (cadr pair) (sum pair)))