2nCn+1{ }^{2 n} C_{n+1}2nCn+1
2nCn{ }^{2 \mathrm{n}} \mathrm{C}_{\mathrm{n}}2nCn
2nCn−1{ }^{2 n} C_{n-1}2nCn−1
2n+1⋅Cn{ }^{2 n+1} \cdot C_{n}2n+1⋅Cn