Problem:
Consider the arithmetic sequence defined by $a_1=\frac{5}{8}$, and $a_n=a_{n-1}+-\sqrt{3}$ for $n > 1$. Compute the nth partial sum, $S_n=\sum_{k=1}^n a_k$, where $n=12$.
Answer:
$6 \left(\frac{5}{4}-11 \sqrt{3}\right)$
{'source': 'AMPS', 'file': 'amps/mathematica/algebra/arithmetic_series/40818.txt'}