Erdős Problem 406 #
Reference: erdosproblems.com/406
theorem
erdos_406.variants.one_two :
IsGreatest {n : ℕ | n.isPowerOfTwo ∧ Nat.digits 3 n ⊆ [1, 2]} (2 ^ 15)
If we only allow the digits $1$ and $2$ then $2^{15}$ seems to be the largest such power of $2$.