Numerical Methods: Euler to Runge–Kutta · Superchallenge problem

Classical RK4 with $n$ steps of size $h = \dfrac{1}{n}$ on $y' = y$, $y(0) = 1$, produces an approximation $Y_n$ to $e$. Find $\displaystyle\lim_{n \to \infty} n^4\,(e - Y_n)$.