For each sequence, find a formula for the general term, $a_n$. For example, answer $n ^2$ if given the sequence:
$\lbrace 1, 4, 9, 16, 25, 36, . . . \rbrace$
$\displaystyle \left\lbrace \frac{1}{2}, \frac{1}{4}, \frac{1}{8}, \frac{1}{16}, \ldots \right\rbrace$
$\displaystyle \left\lbrace \frac{3}{16}, \frac{4}{25}, \frac{5}{36}, \frac{6}{49}, \ldots \right\rbrace$