4. Find a system of recurrence relations to count an, the number of ternary sequences of length n with no consecutive 1s and no consecutive 2s. Then simplify the system to a relation only involving terms of (a). Each element in a ternary sequence is either a 0, 1, or 2. Answer: 5. Find a recurrence relation for the number of quarternary sequences of length n with at least one 1 and the first 1 before the first 0 (possibly no 0s). Each element in a quarternary sequence is either a 0, 1, 2, or 3. Answer: