+ (Spectral) custom bin size - question

So here’s the task:

I want to add up a spread of values so that the resulting spread contains the sum of slices 0-1 in the first slice, the sum of slices 0-2 in the second, the sum of slices 0-3 in the next slice and so on.

I tried to use +(spectral) with a custom bin size but the value get screwed up because the bin size doesn’t seem to always start counting at slice 0. So that if I “ask for” a bin-size of three for the third result-slice, it actually adds the third slice and then adds the other slices from the beginning.

Is there another way to achieve this?

SpectralNotSpectral.v4p (5.8 KB)

This node is called Integral.

There we go. Nice!
Thx for the fast answer!