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-- Largest prime factor
-- Problem 3
-- The prime factors of 13195 are 5, 7, 13 and 29.
-- What is the largest prime factor of the number 600851475143 ?
main = do
print (last $ factors 600851475143)
factors x = trial_division 2 x
trial_division :: Int -> Int -> [Int]
trial_division by x
| x <= 1 = []
| x `mod` by == 0 = by:trial_division by (x `div` by)
| otherwise = trial_division (by + 1) x
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