Knuth [0] discusses in more detail some advantages of indicator notation, in particular that, when you eliminate the limits on summations, it makes it much easi

Knuth [0] discusses in more detail some advantages of indicator notation, in particular that, when you eliminate the limits on summations, it makes it much easier to do algebra on summations. [0] https://arxiv.org/abs/math/9205211 https://arxiv.org/abs/math/9205211