First differences of A007097.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =20a(5) =96a(6) =582a(7) =4672a(8) =47330a(9) =595680a(10) =9088942a(11) =164702708a(12) =3483060060a(13) =84705352206