【简答题】设数列{a n }的前n项和为S n .已知a 1 =1,a n+1 =3S n +1,n∈N * . (Ⅰ)写出a 2 ,a 3 的值,并求数列{a n }的通项公式; (Ⅱ)记T n 为数列{na n }的前n项和,求T n ; (Ⅲ)若数列{b n }满足b 1 =0,b n -b n-1 =log 2 a n (n≥2),求数列{b n }的通项公式.
【简答题】设数列{a n }的前n项和为S n .已知a 1 =1,S n = 1 3 (a n+1 -1) ,n∈N * . (1)写出a 2 ,a 3 的值,并求数列{a n }的通项公式; (2)记 b n = 1 log 4 a n+1 log 4 a n+2 ,数列{b n }的前n项和为T n ,试比较T n 与1的大小.