[postgis-users] How to generate polygon grid for tiled map services

[Gis Mage]

Hi list!

I'm wondering if there is a formula to generate 20 tables (one for
each zoom level) of square polygons, representing a tile grid of
popular TMS like OSM or MapQuest?

I guess there shoud be a way to convert x,y,z tile coordinates to
lat/lon coordinates in PostGIS.