\(\displaystyle \sum_{i,j=0}^{n} {}^{n}C_{i}\,{}^{n}C_{j} \) is equal to \( i\neq j \)
\( 2^{2n}-{}^{2n}C_{n} \)
\(2^{2n-1} - {}^{2n-1}C_{n-1} \)
\( 2^{2n}-\dfrac{1}{2}\,{}^{2n}C_{n} \)
\( 2^{\,n-1}+^{2\,n-1}\,{}^{\, }C_{n} \)