## koli123able Group Title What is the nth term of: 1^2 + (1^2+2^2) + (1^2+2^2+3^2)+..... one year ago one year ago

1. Yahoo! Group Title

$an = \frac{ n(n+1)(2n+1) }{ 6 }$

2. koli123able Group Title

how??

3. SithsAndGiggles Group Title

Do you see how the nth term is something like $1^2+2^2+\cdots+(n-1)^2+n^2?$ What's the sum of all square numbers from 1 to n? i.e., $\sum_{k=1}^n k^2?$