Baking the Y Combinator from Scratch

Is there a technique to remember this? I will understand it today and forget after a few weeks.

It's easier to remember if you use a more common notation:

    (Y(f))(x) = f(f(f(...(x)...)))

Or express it in python, which is still a bit weird but probably still more readable than pure LC to pretty much everybody:

    def Y(f):
        return lambda x: f(Y(f)(x))