In the verse it's just bass but it's fun to play to play the power chords too.  In the 
real song the power chords are only played in the chorus though.  The chord sequence is 
B, A, E, A.

|---------------------------------|
|---------------------------------|
|---------------------------------|
|7-------5-------2-------5--------|
|7-------5-------2-------5--------|
|9-------7-------0-------7--------|

The very simple bit of guitar that's so catchy is on the E string:

|5--5--5-4-5--5--5-4-5--5--5-4-5--5-4-5-4-5|