[Help-glpk] Is anyway to generate a certain subset of the set

[Andy . Zhu]

Hi, here is my problem:

I have defined a set: 
set A := 1 .. N # where N may be 1000
as a param

Is there any easy way to generate all
the N subsets from A as follows:

A1={1}, A2={1,2}, A3={1,2,3} ..., An-1=
{1, ..., N-1}, An={1, 2, ..., N}?

thanks very much.