Let \( f : (-\infty, \infty) - \{0\} \to \) \(\mathbb{R}\) be a differentiable function such that \( f'(1) = \lim_{a \to \infty} a^2 f\!\left(\frac{1}{a}\right) \). Then \( \lim_{a \to \infty} \left[ \dfrac{a(a+1)}{2} \tan^{-1}\!\left(\dfrac{1}{a}\right) \right] + a^2 - 2 \log_e a \) is equal to:

