[Maxima-bugs] [maxima:bugs] #4599 intosum not fully recursive

[Barton W. <wil...@us...>]

OK, how about appending to the user documentation:

For iterated summations, users may need to apply `intosum` repeatedly to move a constant multiplicative factor inside the innermost summation. For example, for the double summation  
`a * sum(sum(f(i, j), j, j0, j1), i, i0, i1)`,  ` intosum` must be applied twice to move `a` inside both summations.




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**[bugs:#4599] intosum not fully recursive**

**Status:** open
**Group:** None
**Labels:** intosum 
**Created:** Fri Aug 22, 2025 01:25 PM UTC by Barton Willis
**Last Updated:** Fri Aug 22, 2025 03:17 PM UTC
**Owner:** nobody


Here we need to apply `intosum` twice.  The user documentation isn't entirely clear about this, but I think that `intosum` isn't fully recursive.

~~~
	(sumexpand  : true, cauchysum  : true, display2d : false)$
	powerseries(exp(x)/(x-5)^n,x,5);
(%o37) ('sum('sum((5^i10*(x-5)^(i9-i10))/(i10!*(i9-i10)!),i10,0,i9),i9,0,inf))

 /(x-5)^n
	intosum(%);
(%o38) 'sum(('sum((5^i10*(x-5)^(i9-i10))/(i10!*(i9-i10)!),i10,0,i9))/(x-5)^n,

            i9,0,inf)
	intosum(%);
(%o39) 'sum('sum((5^i10*(x-5)^(-n+i9-i10))/(i10!*(i9-i10)!),i10,0,i9),i9,0,inf)
~~~


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