Hi Frank,

> Does anyone know how many times (approx.) this sequence occurs in the pali canon?

It's hard to say, since the wording can be various. What matters is that
Buddha pointed out this sequence as one of the key tenets of his
teaching in Mahaparinibbana sutta.

For more refrences see:
http://www.lioncity.net/buddhism/index.php?showtopic=21320&view=findpost&p=312610

Dmytro