a(n) = binomial(A007310(n+1),n)/A007310(n+1).

Terms

a(0) =1a(1) =1a(2) =3a(3) =15a(4) =55a(5) =364a(6) =1428a(7) =10659a(8) =43263a(9) =345345a(10) =1430715a(11) =11920740a(12) =50067108a(13) =429757960a(14) =1822766520a(15) =15991836267a(16) =68328754959a(17) =609599676595