binomial expansion (urgent)

We study $(1+x/n)^n$, x>0.

Write the binomial expansion for $(1+x/n)^n$ as $An^(0)+An^(1)+...+An^(n)$, where $An^(0)=1$ and $An^(n)=(x^n)/(n^n)$.

Give the expression for $An^(k)$.

can someone please help. no idea how to do it.