Answer
$$\eqalign{
& 2,5,12,20,30 \cr
& {\text{The sequence is neither geometric nor arithmetic}} \cr} $$
Work Step by Step
$$\eqalign{
& {a_n} = n\left( {n + 1} \right) \cr
& {\text{Write the first five terms of the sequence}} \cr
& n = 1 \cr
& {a_1} = 1\left( {1 + 1} \right) = 2 \cr
& \cr
& n = 2 \cr
& {a_2} = 2\left( {2 + 1} \right) = 6 \cr
& \cr
& n = 3 \cr
& {a_3} = 3\left( {3 + 1} \right) = 12 \cr
& \cr
& n = 4 \cr
& {a_4} = 4\left( {4 + 1} \right) = 20 \cr
& \cr
& n = 5 \cr
& {a_5} = 5\left( {5 + 1} \right) = 30 \cr
& \cr
& 2,5,12,20,30 \cr
& {\text{The sequence is neither geometric nor arithmetic}} \cr} $$
