Duplicate of A088302.

Terms

a(0) =1a(1) =3a(2) =2a(3) =10a(4) =60a(5) =420a(6) =28a(7) =252a(8) =2520a(9) =27720a(10) =66a(11) =858a(12) =12012a(13) =180180a(14) =2882880a(15) =49008960