2010年江苏省高考19题是一道与等差数列有关的新形式的数列和不等式的综合题,第①小题可以叙述为:性质1设各项均为正数的数列{an}的前n项和为Sn,如果{Sn}是等差数列且a1,a2,a3成等差数列,则数列{an}也是等差数列.具体说明如下.例1(2010年江苏卷19题)设各项均为正数的数列{an}的 2010 Jiangsu Provincial Entrance Examination 19 is a new form of series with the arithmetic progression of inequalities and the integrated problem, the first small problem can be described as: the nature of a set of all the positive sequence {an} n And Sn, if {Sn} is the arithmetic sequence and a1, a2, a3 into arithmetic progression, then the sequence {an} is also an arithmetic sequence as follows: Example 1 (2010 Jiangsu vol 19) set each Items are positive sequence {an}