Given the general term formula of sequence {an} an = n & # 178; + N, then the first n terms of {an} and Sn =?

an =n^2+n
= n(n+1)
= (1/3)[n(n+1)(n+2) - (n-1)n(n+1)]
Sn = (1/3){ summation (i:1->n)[i(i+1)(i+2) - (i-1)i(i+1)] }
= (1/3)n(n+1)(n+2)

RELATED INFORMATIONS

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