To find the fifth term of the sequence defined by the function \( f(n) = 2^n - 1 \), we need to substitute \( n = 5 \) into the function.
\[ f(5) = 2^5 - 1 \]
Calculating \( 2^5 \):
\[ 2^5 = 32 \]
Now substituting that value into the equation:
\[ f(5) = 32 - 1 = 31 \]
Thus, the fifth term of the sequence is
\[ f(5) = 31. \]