Problem:
Consider the arithmetic sequence defined by $a_1=\frac{56}{81}$, and $a_n=a_{n-1}+-\frac{17}{3}$ for $n > 1$. Compute the nth partial sum, $S_n=\sum_{k=1}^n a_k$, where $n=15$.
Answer:
$-\frac{15785}{27}$
{'source': 'AMPS', 'file': 'amps/mathematica/algebra/arithmetic_series/6670.txt'}