14 lines
392 B
Racket
14 lines
392 B
Racket
#lang racket
|
|
|
|
(require math/number-theory)
|
|
|
|
(define (primes x) (filter prime? (range 2 (sqrt x))))
|
|
|
|
(define (primefactors x primes)
|
|
(if (prime? x)
|
|
(list x)
|
|
(if (zero? (remainder x (car primes)))
|
|
(cons (car primes) (primefactors (quotient x (car primes)) primes))
|
|
(primefactors x (cdr primes)))))
|
|
|
|
(apply max (primefactors 600851475143 (primes 600851475143))) |