已知数列{an}满足a1=1,an+1(n+1为下标)=an(n为下标)+n+1求a6

来源:学生作业帮助网 编辑:六六作业网 时间:2024/12/24 09:24:14
已知数列{an}满足a1=1,an+1(n+1为下标)=an(n为下标)+n+1求a6已知数列{an}满足a1=1,an+1(n+1为下标)=an(n为下标)+n+1求a6已知数列{an}满足a1=1

已知数列{an}满足a1=1,an+1(n+1为下标)=an(n为下标)+n+1求a6
已知数列{an}满足a1=1,an+1(n+1为下标)=an(n为下标)+n+1求a6

已知数列{an}满足a1=1,an+1(n+1为下标)=an(n为下标)+n+1求a6
an=a(n-1)+n
……
a2=a1+2
……
an=a1+n+(n-1)+……+2
=a1+[(n-1)(n+2)/2]
=a1+(n²/2)+(n/2)-1
=(n²/2)+(n/2)