Problem 130
http://projecteuler.net/index.php?section=problems&id=130
前問の結果を使えば、楽。
{-# OPTIONS_GHC -XBangPatterns #-} import Number count n = count' n (0,100) 1 count' n (q,r) !k | gcd 10 n /= 1 = n | (q,r)==(0,10) = k | otherwise = count' n (divMod (10*r) (9*n))$ k+1 valid n | mod (n-1) (count n) == 0 = True | otherwise = False main = print.sum.take 25.filter valid$nonprimes