A sequence of numbers starts with 1, 2, and 3. The fourth number of the sequence is the sum of the previous three numbers in the sequence: 1\plus{}2\plus{}3\equal{}6. In the same way, every number after the fourth is the sum of the previous three numbers. What is the eighth number in the sequence?
<spanclass=′latex−bold′>(A)</span>11<spanclass=′latex−bold′>(B)</span>20<spanclass=′latex−bold′>(C)</span>37<spanclass=′latex−bold′>(D)</span>68<spanclass=′latex−bold′>(E)</span>99