Are bluetooth advertise published on one or on at least one channels?
The BLE advertisement uses three channels to avoid interference as explained in this answer. There is no 'channel hopping' as such in advertising, it is used when the BLE device is connected. 

With regards to the channels usage when advertising, it would depend on the BLE stack used and the configuration. For example, the nRF5x Softdevice stack has option to select which of the three channels would be used for advertisements. The default (or examples) option that I have seen is having all the three channels enabled. Which would mean for every advertisement event, the advertisement packet would be sent on the three channels one after the other. Having all three enabled maximizes the chances that an observer listening on one of these three picks it up.