The mathematical notation progression that makes mathematicians achieve transcendence. Starting with the basic "k = 0, ..., n" (how pedestrian), we escalate through increasingly sophisticated set notation until we reach the cosmic brain level of "k ∈ n + 1." Each step represents a mathematician trying to flex their notation muscles harder than the last.
It's like watching someone evolve from saying "I want coffee" to "I desire the aqueous extraction of roasted seeds from the genus Coffea, delivered in a ceramic vessel." Same meaning, exponentially more pretentious. Pure mathematician energy.