5-nonnesting permutations.

Terms

a(0) =1a(1) =2a(2) =6a(3) =24a(4) =120a(5) =720a(6) =5040a(7) =40320a(8) =362856a(9) =3627385a(10) =39864333a(11) =477407104a(12) =6183182389a(13) =86033729930