The sequence that I'm working with is sorta monotonic. It's monotonic most of the time, sometimes there's one number that ruins the trend like 0.0001001 in 0.1, 0.01, 0.001, 0.0001001, 0.0001, ... but those are very rare. Btw, the sequence above is just an example. Is Richardson extrapolation the best method to use in this case? I also have a question about the Richardson extrapolation . I'm gonna call the nth Richardson extrapolation, R(n) Why is it that when I test R(10) on a 30 term sequence, it gives me ridiculous approximations like -5.24 when the actual answer is 1.68?