Find a Formula for the Nth Term of the Sequence $1 , \frac { 1 } { 8 } , \frac { 1 } { 27 } , \frac { 1 } { 64 } , \ldots$

Multiple Choice

Find a formula for the nth term of the sequence. $1 , \frac { 1 } { 8 } , \frac { 1 } { 27 } , \frac { 1 } { 64 } , \ldots$

A) $a ^ { n } = 3 ^ { n }$
B) $a ^ { n } = \frac { 1 } { n ^ { 3 } }$
C) $a ^ { n } = n ^ { 3 }$
D) $a ^ { n } = \frac { 1 } { 3 ^ { n } }$