[r-t] General case of an extent

[Joe Norton]

I was wondering if such a thing has ever been devised as a composition 
of an extent which can be extended to arbitrarily many bells. Either of 
a particular method or of methods with certain lead end groups and clean 
proof.

I guess it's not a thing which would ever have much practical purpose on 
more than, say, 10 or 11 bells but I wondered if anyone had ever come up 
with such a thing.

Thanks,
Joe.