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Sequence: smallest number greater than previous term with exactly n divisors: Difference between revisions
Sequence: smallest number greater than previous term with exactly n divisors (view source)
Revision as of 13:54, 16 July 2020
, 3 years agoadded Haskell
(added Haskell) |
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Line 298:
1 2 4 6 16 18 64 66 100 112 1024 1035 4096 4288 4624
</pre>
=={{header|Haskell}}==
<lang haskell>import Data.List (nub)
import Text.Printf (printf)
divisorCount :: Int -> Int
divisorCount = length . nub . foldr (\(a, b) r -> a:b:r) [] . divisors
where
divisors n = [(x, n `div` x) | x <- [1..ceiling (sqrt $ realToFrac n)], n `mod` x == 0]
sequence_A069654 :: [(Int,Int)]
sequence_A069654 = go 1 nDivCount
where
nDivCount = (,) <*> divisorCount <$> [1..]
go t ((n,d):xs)
| d == t = (d,n) : go (succ t) xs
| otherwise = go t xs
main :: IO ()
main = mapM_ (uncurry(printf "a(%2d)=%5d\n")) $ take 15 sequence_A069654</lang>
{{out}}
<pre>a( 1)= 1
a( 2)= 2
a( 3)= 4
a( 4)= 6
a( 5)= 16
a( 6)= 18
a( 7)= 64
a( 8)= 66
a( 9)= 100
a(10)= 112
a(11)= 1024
a(12)= 1035
a(13)= 4096
a(14)= 4288
a(15)= 4624
</pre>
=={{header|J}}==
<lang j>
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