In one of the Roland campaign scenarios, this number sequence is written on a sign.
Is there anything to this? Some kind of inside joke?

Edit:
Google tells me it's a phone number used in this song:
http://www.youtube.com/watch?v=axLRUszuu9I

It's also a cheat code.

Yeah, all the numbers you find in the game can be used at cheat codes just by entering them. However, if you use them, you will be marker as a cheater in the highscore list so think twice before entering.

It is a cheat code to reveal the entire map - and I use it frequently! There are so many poorly made H2 maps out there and I find the easy way to weed out those that are not worth playing is to take a sneak peak at the map first. If the map is OK I just restart, otherwise I delete it and try another.