findSum :: Integer -> Integer -> Integer -> Integer
findSum a b n = helper a b 2 n 0 0 0
    where
        helper :: Integer -> Integer ->Integer ->
            Integer -> Integer -> Integer -> Integer -> Integer
        helper a b index n first second third
            | index == 2 = helper a b (index+1) (n) (a +b) (a + b+ 2*b) (a + b+ 2*b + 4*b)
            | index >= 3 && index < n = helper a b (index+1) (n) second third (third + (2^index * b))
            | index == n = first + second + third


main::IO()
main=do
    print(findSum 0 2 10)