Write an Expression for the N Th Term of the Sequence

Multiple Choice

Write an expression for the n th term of the sequence $1,3 , \frac { 3 ^ { 2 } } { 2 } , \frac { 3 ^ { 3 } } { 6 } , \frac { 3 ^ { 4 } } { 24 } , \frac { 3 ^ { 5 } } { 120 } , \ldots$ Assume that n begins with 1.

A) $a _ { n } = \frac { 3 ^ { n - 1 } } { n ! }$
B) $a _ { n } = \frac { 3 ^ { n + 1 } } { ( n - 1 ) ! }$
C) $\alpha _ { n } = \frac { 3 ^ { n } } { ( n - 1 ) ! }$
D) $a _ { n } = \frac { 3 ^ { n } } { n ! }$
E) $\alpha _ { n } = \frac { 3 ^ { n - 1 } } { ( n - 1 ) ! }$