Bell(2n)*(2n-1)!!, where Bell are the Bell numbers A000110.

A100101

Bell(2n)*(2n-1)!!, where Bell are the Bell numbers A000110.

Terms

    a(0) =1a(1) =2a(2) =45a(3) =3045a(4) =434700a(5) =109596375a(6) =43800340815

External references