Problem:
Consider the arithmetic sequence defined by $a_1=-\frac{14}{15}$, and $a_n=a_{n-1}+-9$ for $n > 1$. Compute the nth partial sum, $S_n=\sum_{k=1}^n a_k$, where $n=27$.
Answer:
$-\frac{15921}{5}$
{'source': 'AMPS', 'file': 'amps/mathematica/algebra/arithmetic_series/453.txt'}