{...}⟷ℕ

#bijection #one-to-one correspondence #natural numbers #set theory #countable set #mathematical definition

⚖️:y∝xᵏ

#scale invariance #power law relationship #mathematical definition #physics scaling #statistical mechanics #universality

{𝑥}→{𝑓(𝑥)}

#set notation #function notation #input set #output set #mathematical definition