题目:(2006北京高考第20题)在数列{an}中,若a1,a2是正整数,且an=|an-1-an-2|,n=3,4,5,…,则称{an}为绝对差数列.(1)举出一个前5项不为零的绝对差数列(只要写出前10项)(2)若绝对差数列{an}中,a20=3,a21=0,数列{bn}满足bn=an+an+1+an+2,n=1,2,3,…,分别判断当n→∞时,an与bn的极 Title: (2006 Beijing College Entrance Exam Question 20) In the series {an}, if a1, a2 are positive integers, and an=|an-1-an-2|,n=3,4,5,..., then { An} is the absolute difference sequence. (1) Gives the first 5 items of an absolute difference sequence that is not zero (as long as the first 10 items are written). (2) If the absolute difference sequence {an}, a20=3, a21=0 The sequence {bn} satisfies bn=an+an+1+an+2,n=1,2,3,..., and determines the polarity of an and bn when n→∞, respectively.