If y(x) = (x^x)^x, x > 0 then d^2x/dy^2 + 20 at x = 1 is equal to
Let $f : S \to S$ where $S = (0, \infty)$ be a twice differentiable function such that $f(x + 1) = x f(x)$. If $g : S \to \mathbb{R}$ be defined as $g(x) = \log_e f(x)$, then the value of $|g''(5) - g''(1)|$ is equal to :