Logarithmic integral function ($li(x)={\int }_0^x\frac{dt}{\ln t}$, Logarithm integral)

The logarithmic integral function, denoted as \( \mathrm{Li}(x) \), is a special function that is defined as follows: \[ \mathrm{Li}(x) = \int_2^x \frac{dt}{\log(t)} \] for \( x > 1 \). The function is often used in number theory, particularly in relation to the distribution of prime numbers.