Numerical Methods: Euler to Runge–Kutta · Challenge problem

For $y\,\prime = y$, $y(0) = 1$, Euler's method with step $h$ gives $y(1) \approx (1 + h)^{1/h}$. With $h = 0.5$, compute the error $e - (1 + h)^{2}$ to three decimal places.