can somebody post a solution,please?

The solution can easily motivated by the statment of problem and some erdos-szkeers or mirsky's Theorem knowledge.Give each permutation a string $b_1,b_2,\dots ,b_n,a_1,a_2,\dots ,a_n$ where $a_i$ is the length of the largest decreasing subsequence ending in $i$ and $b_i$ is the length of the largest subsequence ending in $i$'th position.It is easy to see that these strings are distinct and since we don't have any decreasing subsequence of length $d$ number of this permutations is at most $(d-1)^{2n}$.