(define (hex x) (if (number? x) (if (zero? x) "0" (let y ((x x) (j 0))
     (if (zero? (modulo x 16)) (y (/ x 16) (+ j 4))
       (string-append (number->string x 16)
         (if (> j 0) (string-append "∙2^" (number->string j 10)) "")))))
   (if (pair? x) (cons (hex (car x)) (hex (cdr x))) '())))

; Bounds on Nd and N.
(let* ((ls arithmetic-shift) (p2 (lambda (n) (ls 1 n))) (÷ quotient))
(list 'N (let sc ((minN (p2 20)) (maxN 0) (minNd (p2 64)) (j (p2 10)))
  (if (< j (p2 11)) (let ((N (÷ (p2 20) (+ j 1))))
      (sc (min minN N) (max maxN N) (min minNd (* N (ls j 42))) (+ j 1)))
    (hex (list minN maxN minNd))))))
; => (N ("2∙2^8" "3ff" "3fd92∙2^44"))