a(n) = A342282(n)/2.

Terms

a(0) =0a(1) =1a(2) =1a(3) =3a(4) =12a(5) =55a(6) =275a(7) =1461a(8) =8121a(9) =46760a(10) =276990a(11) =1679692a(12) =10388794a(13) =65348331a(14) =417122415a(15) =2696925449a(16) =17636415027a(17) =116508178394a(18) =776713914842