Define a sequence

Hi,

Is there a way to define a finite real sequence indexed by integers. I'd like to evaluate an expression such as "u(1)+u(2)" where u is defined by an explicit sequence of real numbers such as u(1)= 12 and u(2)= 25. I don't want to create a finite set a expr u1, u2... More Func object need an algebraic expression.

Best regards.