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

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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
a(n+1)=an+n+1
a(n+1) -an= n+1
an - a(n-1) = n
an - a1 = 2+3+..+n
an = 1+2+..+n = n(n+1)/2
a6 = 21

很简单,令n=1代入求得a2,a1,a2知道,a6还会难吗