Replying to kcrisman:

Maybe it's time we fixed this.

It is not clear if forcing people to use `N()`

and getting a float, even if there is an integer simplification of the sum, is the right thing to do. Granted, the error thrown on `N(I(10))`

is a bug, and this ticket is about it. Here is a minimal example:

sage: (k,n) = var('k,n')
sage: f(n)=sum(abs(-k*k+n),k,1,n)
sage: f(n=8)
sum(abs(-k^2 + 8), k, 1, 8)
sage: N(f(8))

However, I would expect `f(n=8).simplify()`

or `.expand()`

to give me the result `162`

, and this is #17422