I have a question: How does Mathematica compute a derivative numerically by Euler sums in the function "ND", which is found in the numerical calculus package? Which formula is used? Thank you very much!
The "EulerSum" method appears to use Richardson extrapolation (from the description in the documentation).
I don't know why it's called "EulerSum".
Here are some lecture slides that show how to apply Richardson's extrapolation to estimate the derivative (last several slides): https://jmahaffy.sdsu.edu/courses/f16/math541/beamer/richard.pdf. There are other resources that can be googled, too.
Maybe it'll help something.. and this.
