2008AMC12A, 17  Let $$a_{1}$$, $$a_{2}$$, $$\cdots$$ be a sequence determined by the rule $$a_{n}=\frac{a_{n-1}}{2}$$ if $$a_{n-1}$$ is even and $$a_{n}=3a_{n-1}+1$$ if $$a_{n-1}$$ is odd. For how many positive integers $$a_{1}\leqslant 2008$$ is it true that $$a_{1}$$ is less than each of $$a_{2}$$, $$a_{3}$$, and $$a_{4}$$?  令数列$$a_{1}$$, $$a_{2}$$, $$\cdots$$满足: $$a_{n}=\frac{a_{n-1}}{ 2}$$若$$a_{n-1}$$是偶数; $$a_{n}=3a_{n-1}+1$$若$$a_{n-1}$$是奇数。 有多少个正整数$$a_{1}\leqslant 2008$$满足$$a_{1}$$小于$$a_{2}$$, $$a_{3}$$和$$a_{4}$$?
选项为:A:$$250$$  B:$$251$$  C:$$501$$  D:$$502$$  E:$$1004$$  请回答其中一个选项.