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Let $k$ be an even natural number. Show that $3 ^ k + 1$ is divisible by $2$ but not by $4$.

Replace sorry in the template below with your solution. The Mathlib version currently used is v4.26.0.

import Mathlib.Algebra.Ring.Parity

theorem solution (k : ℕ) (hk : Even k) : 2 ∣ 3 ^ k + 1 ∧ ¬ 4 ∣ 3 ^ k + 1 := sorry

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