A series combination of \(n_1\) capacitors, each of value \(C_1\), is charged by a source of potential difference \(4V\). When another parallel combination of \(n_2\) capacitors, each of value \(C_2\), is charged by a source of potential difference \(V\), it has the same (total) energy stored in it, as the first combination has. The value of \(C_2\), in terms of \(C_1\), is then