a(n) = C(n+2,2)*C(n,floor(n/2)).

Terms

a(0) =1a(1) =3a(2) =12a(3) =30a(4) =90a(5) =210a(6) =560a(7) =1260a(8) =3150a(9) =6930a(10) =16632a(11) =36036a(12) =84084a(13) =180180a(14) =411840a(15) =875160a(16) =1969110a(17) =4157010a(18) =9237800a(19) =19399380a(20) =42678636a(21) =89237148a(22) =194699232a(23) =405623400a(24) =878850700a(25) =1825305300a(26) =3931426800a(27) =8143669800a(28) =17450721000