My Objective Function is the following:

@setObjective(m,Min, sum{costs[i,j]*x[i,j,k,t],i= nodes, j = nodes, k = vehicles, t = periods})

AND I would like to make “i < j” in the sum expression above! It is like adding a constraint on the indexes only for this expression. Is this possible? How is the syntax?

Thank you very much.