I believe you may have entered a mathematical expression or notation, but it's not quite clear. Could you please provide more context or clarify what you're trying to calculate or express?

If you meant "18 choose 2" (a combination in mathematics), it would typically be written as \( C(18, 2) \) or \( \binom{18}{2} \).

The formula for combinations is:

\[ C(n, k) = \frac{n!}{k!(n-k)!} \]

So, for \( C(18, 2) \):

\[ C(18, 2) = \frac{18!}{2!(18-2)!} = \frac{18!}{2! \cdot 16!} = \frac{18 \times 17}{2 \times 1} = 153 \]

Is this what you were asking about? If not, could you please provide more details?