Let \(V_{r}\) denote the sum of \(1^{\text{st}\text{~}}r\) terms of an arithmetic progression (A.P.) whose \(1^{\text{st}\text{~}}\) . term is \(r\) and the common difference is \(2r - 1\). Let \(T_{r} = V_{r + 1} - V_{r}\) and \(Q_{r} = T_{r + 1} - {T}_{r}\) for \(r = 1,2,\ldots\) \(T_{r}\) is always a/an