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Concatenate two primes is also prime: Difference between revisions
Concatenate two primes is also prime (view source)
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Found 128 such concatenated primes.
</pre>
=={{header|Haskell}}==
<lang haskell>import Control.Applicative
import Data.List ( sort )
import Data.List.Split ( chunksOf )
isPrime :: Int -> Bool
isPrime n
|n == 2 = True
|n == 1 = False
|otherwise = null $ filter (\i -> mod n i == 0 ) [2 .. root]
where
root :: Int
root = floor $ sqrt $ fromIntegral n
solution :: [Int]
solution = sort $ filter isPrime $ map read ( (++) <$> numberlist <*> numberlist )
where
numberlist :: [String]
numberlist = map show $ filter isPrime [1 .. 99]
main :: IO ( )
main = do
mapM_ print $ chunksOf 15 solution</lang>
{{out}}
<pre>
[23,37,53,73,113,137,173,193,197,211,223,229,233,241,271]
[283,293,311,313,313,317,317,331,337,347,353,359,367,373,373]
[379,383,389,397,433,523,541,547,571,593,613,617,673,677,719]
[733,743,761,773,797,797,977,1117,1123,1129,1153,1171,1319,1361,1367]
[1373,1723,1741,1747,1753,1759,1783,1789,1913,1931,1973,1979,1997,2311,2341]
[2347,2371,2383,2389,2917,2953,2971,3119,3137,3167,3719,3761,3767,3779,3797]
[4111,4129,4153,4159,4337,4373,4397,4723,4729,4759,4783,4789,5323,5347,5923]
[5953,6113,6131,6143,6173,6197,6719,6737,6761,6779,7129,7159,7331,7919,7937]
[8311,8317,8329,8353,8389,8923,8929,8941,8971,9719,9743,9767]
</pre>
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