We have initial conditions: $n_1=2, v_1=1.$ And given recurrence relations: $v_i=(2^{i+1}+1) v_{i-1}$ $n_i=2^i n_{i-1}+v_{i-2}+v_{i-1}$ I need to prove the below lower bound: $$v_i≥n_i.e^{\Omega(\sqrt{\log n_i})}.$$ Is there any easy way to solve it? I have no clue to solve.