# A permutation problem

Discrete Mathematics Level pending

Let A={1,2,…,n}. For a permutation P = { P(1) , P(2) , … , P(n) } of the elements of A, let P(1) denote the first element of P. Find the number of all such permutations P so that for that all i,j∈A if i < j < P(1) then j appears before i in P if P(1) < i< j then i appears before j in P

×