a(n) = A324488(n)/n.

Terms

a(0) =1a(1) =0a(2) =21a(3) =31a(4) =266a(5) =672a(6) =3484a(7) =11375a(8) =48768a(9) =177023a(10) =716418a(11) =2730315a(12) =10878520a(13) =42485638a(14) =169181010a(15) =670042125a(16) =2678678730a(17) =10705526976a(18) =43007270292a(19) =173003915322a(20) =698235680844