simp only [cast_add, cast_one, cast_mul, cast_pow, ← Real.rpow_natCast]
n : ℕ
n_large : 512 ≤ n
⊢ ↑(n * (2 * n) ^ (2 * n).sqrt * 4 ^ (2 * n / 3)) ≤ ↑(4 ^ n)
n : ℕ
n_large : 512 ≤ n
⊢ ↑n * (↑2 * ↑n) ^ ↑(2 * n).sqrt * ↑4 ^ ↑(2 * n / 3) ≤ ↑4 ^ ↑n