[Maxima-bugs] [maxima:bugs] #4634 Divergent integral simplifies to -1/4 with simplify_sum

[kcrisman <kcr...@us...>]

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**[bugs:#4634] Divergent integral simplifies to -1/4 with simplify_sum**

**Status:** open
**Group:** None
**Created:** Tue Nov 18, 2025 12:58 PM UTC by kcrisman
**Last Updated:** Tue Nov 18, 2025 12:58 PM UTC
**Owner:** nobody


In the [Sage support list](https://groups.google.com/g/sage-support/c/pCYoD6x2Y8M) we have the following message about a divergent integral giving a solution with the optional package `simplify_sum`.

"In maxima 5.47.0 I get:

```
(%i1) load(simplify_sum)$
(%i2) simplify_sum( sum(n*(-1)^n,n,1,inf));
-1/4
```

This happens both on sage's ECL based one and on the system maxima (running on SBCL). "

That this is a reversion is seen from the following:

```
Maxima 5.42.2 http://maxima.sourceforge.net
using Lisp ECL 16.1.2
Distributed under the GNU Public License. See the file COPYING.
Dedicated to the memory of William Schelter.
The function bug_report() provides bug reporting information.
(%i1) load(simplify_sum)$

(%i2) simplify_sum( sum(n*(-1)^n,n,1,inf));
(%o2)                                 ind
```



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