Indivisibility of binomial coefficients

Let us denote by C_n^i the binomial coefficient where 0 \leq i \leq n and $n$, $i$ are integers. Given a natural number $n$ and a prime number $p$, find the number of integers $i$ from \{0, 1, \ldots, n\} such that C_n^i is not divisible by $p$.