Solution:
We have the recurrence En=21(En−1+1)+21(En−2+1), or En=1+21(En−1+En−2), for n≥2.
Let Fn=En−32n. By directly plugging this into the recurrence for En, we get the recurrence Fn=21(Fn−1+Fn−2). The roots of the characteristic polynomial of this recurrence are 1 and −21, so Fn=A+B(−21)n for some A and B depending on the initial conditions. But clearly we have E0=0 and E1=1 so F0=0 and F1=31 so A=92 and B=−92.
Hence, En=32n+92−92(−21)n, so limn→∞(En−32n−92)=0. Hence (32,92) is the desired pair.