题目

-- Don’t you think hard work is what makes people succeed? -- ________________ A．I couldn’t agree more                            B．I hope so  C．I’ve got it                               D．Wish you success 答案：A数列{an}中，a3=1，a1+a2+…+an=an+1（n=1，2，3…）．（Ⅰ）求a1，a2；（Ⅱ）求数列{an}的前n项和Sn；（Ⅲ）设bn=log2Sn，存在数列{cn}使得cn•bn+3•bn+4=1+n（n+1）（n+2）Sn，试求数列{cn}的前n项和．