倍数になる13進数
s13 s = sum $ map (\(y,z) -> (13 ^ y) * (read [z])) $ zip [(length s)-1,(length s)-2..0] s f = [n | n <- [10..], n * 2 == s13 (show n)]
s13 s = sum $ map (\(y,z) -> (13 ^ y) * (read [z])) $ zip [(length s)-1,(length s)-2..0] s f = [n | n <- [10..], n * 2 == s13 (show n)]