Question 17
(FRG 3) In a permutation $(x_1,x_2,\ldots,x_n)$ of the set $1,2,\ldots,n$ we call a pair $(x_i,x_j)$ discordant if $i\lt j$ and $x_i\gt x_j$. Let $d(n,k)$ be the number of such permutations with exactly $k$ discordant pairs. Find $d(n,2)$ and $d(n,3)$.