Status: Valid
Owner: ----
Labels: Type-Defect Priority-High Integration Concrete

New issue 3998 by ronan.l...@gmail.com: summation(x**n/n, (n, 1, 400)) hangs
http://code.google.com/p/sympy/issues/detail?id=3998

summation(x**n/n, (n, 1, 400)) now hangs, instead of returning the same thins as sum([x**n/n for n in range(1, 401)]) like it used to.

Control-Cing it shows that the hang-up happens while calling eval_sum_hyper.

In [2]: expr = summation(x**n/n, (n, 1, 400))
^C---------------------------------------------------------------------------
KeyboardInterrupt                         Traceback (most recent call last)
<ipython-input-2-4f1ee74508b7> in <module>()
----> 1 expr = summation(x**n/n, (n, 1, 400))

/home/ronan/devel/sympy/sympy/concrete/summations.py in summation(f, *symbols, **kwargs)
    444
    445     """
--> 446     return Sum(f, *symbols, **kwargs).doit(deep=False)
    447
    448

/home/ronan/devel/sympy/sympy/concrete/summations.py in doit(self, **hints)
    248                 f = -f
    249
--> 250             newf = eval_sum(f, (i, a, b))
    251             if newf is None:
    252                 if f == self.function:

/home/ronan/devel/sympy/sympy/concrete/summations.py in eval_sum(f, limits)
    548     # this can save time when b-a is big.
    549     # We should try to transform to partial fractions
--> 550     value = eval_sum_symbolic(f.expand(), (i, a, b))
    551     if value is not None:
    552         return value

/home/ronan/devel/sympy/sympy/concrete/summations.py in eval_sum_symbolic(f, limits)
    642             return r
    643
--> 644     return eval_sum_hyper(f, (i, a, b))
    645
    646


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