TAFD33 by Hoya

$$n(\lambda) = \sqrt{3.4317 - 0.0131563\,\lambda^2 + 0.0356319\,\lambda^{-2} + 0.000913781\,\lambda^{-4} - 4.03669 \times 10^{-6}\,\lambda^{-6} + 3.38677 \times 10^{-6}\,\lambda^{-8}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[1.04 \times 10^{-6} + 2(9.9 \times 10^{-9})\,\Delta T + 3(-5.86 \times 10^{-11})\,\Delta T^2 + \frac{9.55 \times 10^{-7} + 2(8.81 \times 10^{-10})\,\Delta T}{\lambda - 0.159}\right] \Delta T = T - T_0, \quad T_0 = 23\,°\text{C}$$