Dear sympy,
My teaching assistant found this bug while preparing some exercices on
sympy:
In [1]: from sympy import summation, oo, simplify
In [2]: from sympy.abc import j
In [3]: s = summation(j/((j+2)*(j+4)*(j+8)), (j, 1, oo))
In [4]: s
Out[4]: 4*(-526 + 484*exp_polar(0))/(225*(-672 + 672*exp_polar(0))) +
7*(-73 + 85*exp_polar(0))/(225*(-336 + 336*exp_polar(0)))
In [5]: simplify(s)
Out[5]: 521/25200
In [6]: _.n()
Out[6]: 0.0206746031746032
In [7]: 4/35.
Out[7]: 0.11428571428571428
In [8]: import sympy
In [9]: sympy.__version__
Out[9]: '0.7.6.1'
┌────────────────────────────────────────────────────────────────────┐
│ SageMath Version 7.1.beta3, Release Date: 2016-02-11 │
│ Type "notebook()" for the browser-based notebook interface. │
│ Type "help()" for help. │
└────────────────────────────────────────────────────────────────────┘
┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
┃ Warning: this is a prerelease version, and it may be unstable. ┃
┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
sage: j = var('j')
sage: sum(j/((j+2)*(j+4)*(j+8)), j, 1, oo)
4/35
Cheers,
Sébastien Labbé
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