Thanks for all the help from everyone!

How do repeat a number 3 times? I tried adding the following in Column A:
A1: 1
A2: 2
A3: 3

But when I dragged it down, it didnt repeat them perfect. In some places it was missing a number....

I just need this:
1
2
3
1
2
3
1
2
3
etc...

Thanks!