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module Y2018.M02.D19.Exercise where
{--
From Fermat's Library @fermatslibrary
https://twitter.com/fermatslibrary/status/964139748230160389
A permutable prime is a prime number which, in a given base, can have its
digits' positions switched through any permutation and still be a prime number.
The largest known is (10^278343-1)/9.
991 is prime
199 is prime
919 is prime
Find the permutable primes in range n
--}
import Data.Set (Set)
permutablePrimes :: Int -> Set (Set Int)
permutablePrimes n = undefined
{--
>>> last (Set.toList $ permutablePrimes 200)
fromList [199,919,991]
How many coprime sets are there up to 100? up to 1000?
--}