\[a_{n} = \frac{n - 1}{n²}\]
\[a_{1} = 0\]
\[a_{2} = \frac{2 - 1}{4} = \frac{1}{4}\]
\[a_{3} = \frac{3 - 1}{9} = \frac{2}{9}\]
\[a_{4} = \frac{4 - 1}{16} = \frac{3}{16}\]