lucky.hs

import System.Environment
import Data.List (intercalate)

killEvery :: Int -> Int -> [a] -> [a]
killEvery n start = go start
 where
    go 0 (_:xs) = go (pred n) xs
    go i (x:xs) = x : go (pred i) xs
    go _ [] = []

lucky :: [Int]
lucky = 1 : go 2 [3, 5 ..]
 where
    go idx (x:xs) = x : go (succ idx) (killEvery x (x-idx-1) xs)

sample n = takeWhile (< n) lucky

csv xs = intercalate "," $ map (show . show) xs

main = do
    as <- getArgs
    case as of
        ["--until", n] -> do
            putStr . unlines . map show $ sample (read n)
        [] -> do
            putStr . unlines . map show $ lucky