C

n=sqrt(1+4.35+5.08/(1-pow(18.76/x,2)))

Python

n=(1+4.35+5.08/(1-(18.76/x)**2))**.5

Fortran

n=SQRT(1+4.35+5.08/(1-(18.76/x)**2))

MATLAB

n=sqrt(1+4.35+5.08./(1-(18.76./x).^2))

LaTeX

n^2-1=4.35+\frac{5.08λ^2}{λ^2-18.76^2}