a(n) = A143702(n)/2.

Terms

a(0) =1a(1) =3a(2) =7a(3) =15a(4) =15a(5) =21a(6) =15a(7) =39a(8) =91a(9) =555a(10) =285a(11) =915a(12) =3333a(13) =1155a(14) =1267a(15) =2769a(16) =4935a(17) =10005a(18) =70635a(19) =7035a(20) =240045a(21) =77745a(22) =167055a(23) =897429a(24) =1231635a(25) =1066065a(26) =1174695