Если интеерсно - программка:

import List

all_bits max n = all [] max 0 n where 
    all hd max _ 0 = [hd]
    all hd max i n | i == max   = []
                   | otherwise  = (all (i:hd) max (i+1) (n-1))++(all hd max (i+1) n)

min_p l = head [ p  | p <- [length l..], (not . dups . sort . map (`mod` p)) l  ] where
    dups [] = False
    dups [_] = False
    dups (a:b:c) | a == b = True
                 | otherwise = dups (b:c)


mid l = sum (map (fromInteger . toInteger) l) / ((fromInteger . toInteger) (length l))

main = mapM_ putStrLn [ "N=" ++ show n ++ " k=" ++ show k ++ 
                        "  p=" ++ ((show . mid . map min_p . sort) (all_bits n k)) 
                        | n <- [10, 20, 30], k <- [2..6] ]