It’s worth pointing out that there is a closed form for the sum of a finite geometric series used for summing harmonic sine waves into bandlimited impulse train

It’s worth pointing out that there is a closed form for the sum of a finite geometric series used for summing harmonic sine waves into bandlimited impulse trains (BLIT) which are filtered to create alias-free classic analog oscillators: https://ccrma.stanford.edu/~stilti/papers/blit.pdf https://ccrma.stanford.edu/~stilti/papers/blit.pdf