Given a sequence a(n) = n / [(n^2)+4]

I know that:

A sequence is bounded if a K∈R exists so that the the absolute value of the sequence |a(n)| for every n∈N smaller than K is. -- |a(n)| <= K

How can i prove this? Picking a random K won't do, i guess, so how would you go about doing it?

thank you