Composing adaptors in Boost::range

I started playing with Boost::Range in order to have a pipeline of lazy transforms in C++. My problem now is how to split a pipeline in smaller parts. Suppose I have:

int main(){
  auto map = boost::adaptors::transformed; // shorten the name
  auto sink = generate(1) | map([](int x){ return 2*x; })
                          | map([](int x){ return x+1; })
                          | map([](int x){ return 3*x; });
  for(auto i : sink)
    std::cout << i << "\n";
}

And I want to replace the first two maps with a magic_transform, i.e.:

int main(){
  auto map = boost::adaptors::transformed; // shorten the name
  auto sink = generate(1) | magic_transform()
                          | map([](int x){ return 3*x; });
  for(auto i : sink)
    std::cout << i << "\n";
}

How would one write magic_transform? I looked up Boost::Range's documentation, but I can't get a good grasp of it.

Addendum: I'm looking to write a class like this:

class magic_transform {
    ... run_pipeline(... input) {
        return input | map([](int x){ return 2*x; })
                     | map([](int x){ return x+1; });
};