Question

The $n^{th}$ term of the sequence 1, 3, 7, 15,... can be written as $2^n-1$.

• A. $2^n-1$.
• B. $2^n+1$.
• C. $3^n-1$.
• D. $3^n+1$.

Answer 1

The correct option is A

$2^n-1$.

The terms can be written as

($2^1$ - 1),( $2^2$ - 1), ( $2^3$ - 1).............

$\Rightarrow$ $n^{th}$ term = $2^n$ - 1