S-NPH5 by Ohara

$$n(\lambda) = \sqrt{1 + \frac{1.89109\,\lambda^2}{\lambda^2 - 0.0141164} + \frac{0.39522\,\lambda^2}{\lambda^2 - 0.0662834} + \frac{2.20492\,\lambda^2}{\lambda^2 - 148.681}}$$

$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[-3.54 \times 10^{-6} + 2(1.02 \times 10^{-8})\,\Delta T + 3(-1.58 \times 10^{-11})\,\Delta T^2 + \frac{9.61 \times 10^{-7} + 2(1.36 \times 10^{-9})\,\Delta T}{\lambda - 0.313}\right] \Delta T = T - T_0, \quad T_0 = 25\,°\text{C}$$