1. (2020高三上·湖州月考) 有如下VB程序段：

a(1) = 1: s = 0

For i = 2 To 6

 s = 0

 For j = 1 To i – 1

   s = s + a(j)

 Next j

 a(i) = s + 1

Next i

执行该程序段后，a(6)的值为（   ）