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# Behavior of symbolic_sum changed?

Consider

from sage.calculus.calculus import symbolic_sum
n = var('n')
print 1/(1 + symbolic_sum(factorial(n) * x^n, n, 1, oo))


Answer of Sage 7.4:

1/(x*hypergeometric((1, 2), (), x) + 1)


Answer of Sage 8.0:

ValueError: Computation failed since Maxima requested
additional constraints; ....

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Expand the traceback. You'll see that "assume ... may help" (or words to that effect). Indeed:

from sage.calculus.calculus import symbolic_sum
n = var('n')
var('x'); assume(x==0)
print 1/(1 + symbolic_sum(factorial(n) * x^n, n, 1, oo))


gives the answer you got in 7.4:

1/(x*hypergeometric((1, 2), (), x) + 1)


However, if we assume (x>0) or assume (x<0), we get "Sum divergent".

The short answer: Maxima was up-rev'd with sage-8.0 to maxima-5.39.0 and may exhibit different behavior from previous versions.

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Asked: 2017-08-11 12:56:28 -0500

Seen: 88 times

Last updated: Aug 11 '17