RE: HP48-HP50G : Error functions ERF(z), FRESNEL integrals, PROBIT, etc.

[Gil]

From Wikipedia, we can write the following program, with z a complex number:

erf(z)
« —> z
« 'Sum(n=0,50,(-1)^n/((2*n+1)*n!)*z^(2*n+1))' 2 * SQRT(PI) /
—>NUM
»
»

Note that a loop of 50, 60 or 100 does not make a real difference, because of the roundings.

Most of the given digits are correct, but not all.

However, even for z complex, the error function erf(z) of the HP Prime gives all the digits correct.
Does somebody know how (which algorithm) the HP Prime proceeds to obtain such a performance?