; torn numbers

(define (torn? n)
  (define (square x) (* x x))
  (let loop ((ten-power 10))
    (if (< n ten-power) #f
      (let ((a (quotient n ten-power))
            (b (modulo n ten-power)))
        (if (= (square (+ a b)) n) #t
          (loop (* ten-power 10)))))))

(do ((n 10 (+ n 1))) (#f)
  (when (torn? n) (display n) (newline)))

81
100
2025
3025
9801
10000
88209
494209
998001
1000000

Timeout