看拼音写汉字。
yù
píng
jì shéng
chá
wēi xiǎn
shùn
养____
花____
____
____叶
____序
liǎ
suǒ
jī
dǔ
huò
____人
____道
____动
____住
____得
This is ______ eraser. That is ______ ruler.
已知数列{an}的前n项和为Sn,且a1=1,Sn=an+1﹣1,则an=____