symsum does not work with symprod

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Adam Golinski
Adam Golinski 2023-3-1
评论： Adam Golinski 2023-3-3
I'm trying to avaluate the following:
syms j k
double(symsum((-symprod((j+0.3-1)/(j), j, 1,k))^2, k, 2, Inf))
It returns: -0.0806, which is nonsensical, since this is a sum of squared numbers.
When I evaluate the same in Wolfram Alpha using "sum( (product (j+0.3-1)/j, j=1..k)^2, k, 2, infinity)", I get 0.226456, which seems to be correct, since Matlab seems to converge to this number up to k=100000 (and then it crushes). How can I make it work? Thanks.

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Walter Roberson
Walter Roberson 2023-3-1
Ran in:
syms j k
double(symsum((-symprod((j+0.3-1)/(j), j, 1,k))^2, k, 2, Inf))
ans = 0.2265
So it works in current releases.
I am checking back to see if I can figure out when it was fixed.
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Walter Roberson
Walter Roberson 2023-3-1
Works in R2018b.
It appears that R2018a is the last release that has this problem.
It is a problem with the symsum() part, by the way; it is returning a hypergeom() minus a constant when it should be returning an expression in gamma() minus that same constant.
Adam Golinski
Adam Golinski 2023-3-3
Walter, many thanks for your help. I've installed a new version and it works now indeed. Best wishes!

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