⇣ primitive roots

⇡ 5 is a primitive root modulo 3ᵏ

⇡ 1, 2, 4, pᵏ, 2·pᵏ

⇡ pᵏ − pᵏ⁻¹

⇡ φ(p − 1)

⇡ φ(φ(n))

⇡ primitive roots and Miller-Rabin