Sage incorrectly evaluates series

proy87
47 ●4 ●6

tmonteil
27483 ●32 ●205 ●519 http://wiki.sagemath.o...

It incorrectly evaluates $\displaystyle\sum_{n=0}^{\infty}\frac{1}{((2n+1)^2-4)^2}=\frac{\pi^2}{64}-\frac{1}{12}$ , but correct answer is $\displaystyle\frac{\pi^2}{64}$

answered 8 years ago

Sébastien
3321 ●8 ●44 ●91 http://www.slabbe.org/

updated 8 years ago

Indeed:

sage: n = var('n')
sage: sum(1/((2*n+1)^2-4)^2, n, 0, Infinity)
1/64*pi^2 - 1/12

See ticket #22005. Mathematica does it correctly:

sage: sum(1/((2*n+1)^2-4)^2, n, 0, Infinity, algorithm='mathematica')
1/64*pi^2

Giac gives this:

sage: sum(1/((2*n+1)^2-4)^2, n, 0, Infinity, algorithm='giac')
1/32*Psi(-1/2, 1) - 1/8

And SymPy seems to do it correctly:

sage: from sympy.abc import n
sage: from sympy import summation, oo
sage: A = summation(1/((2*n+1)^2-4)^2, (n, 0, oo))
sage: A._sage_()
1/64*pi^2

I created ticket #22004 so that one can do:

sage: sum(1/((2*n+1)^2-4)^2, n, 0, Infinity, algorithm='sympy')
1/64*pi^2

link

Comments

Thanks! We should also file an upstream bug report at Maxima - can you do that as well?

kcrisman ( 8 years ago )

I do not not have a account on the sourgeforge of maxima. Also I do not have access to version latest version 5.38. If possible, I will let somebody else do the upstream bug report.

Sébastien ( 8 years ago )

Thanks for the ticket !

tmonteil ( 8 years ago )

This may actually be https://sourceforge.net/p/maxima/bugs... which is apparently fixed in upstream.

kcrisman ( 8 years ago )

I've got ValueError: Mathematica cannot make sense of input sum(1/((2*x+1)^2-4)^2,x,0,Infinity, algorithm='mathematica')

proy87 ( 8 years ago )

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