6 The sequence $a_{n}$ satisfy $a_{n}=a_{n-1}+n^{2}$ and $a_{0}=2009$. Find $a_{\text {so }}$.
(A) 42434
(B) 42925
(C) 44934
(D) 45029
(E) 45359
$6 \quad$ Answer: (C)
Let $b_{n}=a_{n}-a_{n-1}=n^{2} . \sum_{n=1}^{50} b_{n}=\sum_{n=1}^{50} n^{2}=\frac{20}{100}(50)(51)(101)=42925$.
On the other hand, $\sum_{n=1}^{50} b_{n}=a_{50}-a_{0} \Rightarrow a_{50}=42925+a_{0}=44934$.