collatzR n 
        | n `mod` 2 == 0 = n : collatzR (n `div` 2)
        | otherwise = n : collatzR (3*n + 1)
collatzR n 
        | n `mod` 2 == 0 = n : collatzR (n `div` 2)
        | otherwise = n : collatzR (3*n + 1)
collatzR n 
        | n `mod` 2 == 0 = n : collatzR (n `div` 2)
        | otherwise = n : collatzR (3*n + 1)