E1 Ei En Li Spence

Li() Function Li ( X As  Double, Optional Info As  Long  ) Logarithmic integral li(x) Purpose This routine computes the logarithmic integral li(x). li(x) = integral 1/ln(t) dt [0, x] = Ei(ln(x)) Returns Double Logarithmic integral li(x). Parameters [in] X Argument x. (X >= 0) [out] Info (Optional) = 0: Successful exit. = -1: The argument X had an illegal value. (X < 0) = 1: Floating point range error. Reference boost/math/special_functions