Another problem for GoT

[Jakkace]

What is the least number of weights that can be used on a scale pan to weigh any integral number of pounds from 1 to 40 inclusive, if the weights can be placed in either of the scale pans?

[The Armchair]

I'm pretty sure I already asked this one. And mine had a little story to go along with it /images/graemlins/smile.gif