Real Sequence/Examples/(-1)^n 2^(-n)

Examples of Real Sequence
The real sequence whose first few terms are:


 * $1, -\dfrac 1 2, \dfrac 1 4, -\dfrac 1 8, \dotsc$

can be defined by the formula:
 * $S = \sequence {\paren {-1}^n \dfrac 1 {2^n} }_{n \mathop \ge 0}$