There are 4 na's. I take this to be as though you're singing the chorus of a Kaiser Chiefs song (na na na na) with the stress on the 'n' of the 'na' rather than on the 'a' by elongating its sound.

So where ' = primary stress, something like this:

Da'na'na'na'naykroyd

Is that correct? I've been saying it far too much out loud and now it sounds silly.