题目

这种东西近来需求量不大。There isn't much such things these days. 答案：【1】call for已知数列{an}满足a1=1，an+1=3an3+2an．设bn=anan+1-19，Sn=b1+b2+…+bn．（Ⅰ）求数列{an}的通项公式；（Ⅱ）求证：Sn≤32（n≤N*）．