One problem you face is the essential singularity, so getting an expansion valid _around_ x=0 of erf(1/x) will be difficult. However, there is a continued fraction in Abramowitz & Stegun, formula 7.1.4, which you might be able to work with. 2 e^z^2 integral( z to infinity, e^-t^2 dt) = 1/(z+ (1/2)/( z+ 1/( z + (3/2)/(z + 2/(z+ ... ))))) supposedly valid for Re(z)>0. After the first 1, 1/2, the numerators are just stepping by 1/2. This makes the convergence somewhat dawdling for small z (and eventually for any z), but it should work for your range of interest. Rich ------------------ Quoting wouter meeussen <wouter.meeussen@pandora.be>:
dear math funners,
does anyone know of a series development of erf(x) round x-> infinity, or equivalently series of erf (1/x) around x=0? Alternatively, how to get approximations to log(1-erf(x)) for x around, say, 50 to 1000? Googled for it in vain,
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